[libc] Add functions to send/recv messages (#106467)

This patch adds the necessary functions to send and receive messages
over a socket. Those functions are: recv, recvfrom, recvmsg, send,
sendto, sendmsg, and socketpair for testing.

libc/config/linux/api.td

@@ -193,6 +193,10 @@ def SysSocketAPI : PublicAPI<"sys/socket.h"> {
     "socklen_t",
     "struct sockaddr",
     "struct sockaddr_un",
+    "struct msghdr",
+    "struct iovec",
+    "size_t",
+    "ssize_t",
   ];
 }
 

libc/config/linux/x86_64/entrypoints.txt

@@ -1041,8 +1041,14 @@ if(LLVM_LIBC_FULL_BUILD)
     libc.src.sys.select.select
 
     # sys/socket.h entrypoints
-    libc.src.sys.socket.bind
     libc.src.sys.socket.socket
+    libc.src.sys.socket.socketpair
+    libc.src.sys.socket.send
+    libc.src.sys.socket.sendto
+    libc.src.sys.socket.sendmsg
+    libc.src.sys.socket.recv
+    libc.src.sys.socket.recvfrom
+    libc.src.sys.socket.recvmsg
   )
 endif()
 

libc/hdr/types/CMakeLists.txt

@@ -199,3 +199,30 @@ add_proxy_header_library(
     libc.include.setjmp
 )
 
+
+add_proxy_header_library(
+  struct_msghdr
+  HDRS
+    struct_msghdr.h
+  FULL_BUILD_DEPENDS
+    libc.include.llvm-libc-types.struct_msghdr
+    libc.include.sys_socket
+)
+
+add_proxy_header_library(
+  struct_sockaddr
+  HDRS
+    struct_sockaddr.h
+  FULL_BUILD_DEPENDS
+    libc.include.llvm-libc-types.struct_sockaddr
+    libc.include.sys_socket
+)
+
+add_proxy_header_library(
+  socklen_t
+  HDRS
+    socklen_t.h
+  FULL_BUILD_DEPENDS
+    libc.include.llvm-libc-types.socklen_t
+    libc.include.sys_socket
+)

libc/hdr/types/socklen_t.h

@@ -0,0 +1,21 @@
+//===-- Proxy for socklen_t -----------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_LIBC_HDR_TYPES_SOCKLEN_T_H
+#define LLVM_LIBC_HDR_TYPES_SOCKLEN_T_H
+
+#ifdef LIBC_FULL_BUILD
+
+#include "include/llvm-libc-types/socklen_t.h"
+
+#else
+
+#include <signal.h>
+
+#endif // LIBC_FULL_BUILD
+
+#endif // LLVM_LIBC_HDR_TYPES_SOCKLEN_T_H

libc/hdr/types/ssize_t.h

@@ -0,0 +1,23 @@
+//===-- Proxy for ssize_t -------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_LIBC_HDR_TYPES_SSIZE_T_H
+#define LLVM_LIBC_HDR_TYPES_SSIZE_T_H
+
+#ifdef LIBC_FULL_BUILD
+
+#include "include/llvm-libc-types/ssize_t.h"
+
+#else
+
+#define __need_ssize_t
+#include <stddef.h>
+#undef __need_ssize_t
+
+#endif // LIBC_FULL_BUILD
+
+#endif // LLVM_LIBC_HDR_TYPES_SSIZE_T_H

libc/hdr/types/struct_msghdr.h

@@ -0,0 +1,21 @@
+//===-- Proxy for struct msghdr  ------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_LIBC_HDR_TYPES_STRUCT_MSGHDR_H
+#define LLVM_LIBC_HDR_TYPES_STRUCT_MSGHDR_H
+
+#ifdef LIBC_FULL_BUILD
+
+#include "include/llvm-libc-types/struct_msghdr.h"
+
+#else
+
+#include <sys/socket.h>
+
+#endif // LIBC_FULL_BUILD
+
+#endif // LLVM_LIBC_HDR_TYPES_STRUCT_MSGHDR_H

libc/hdr/types/struct_sockaddr.h

@@ -0,0 +1,21 @@
+//===-- Proxy for struct sockaddr  ----------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_LIBC_HDR_TYPES_STRUCT_SOCKADDR_H
+#define LLVM_LIBC_HDR_TYPES_STRUCT_SOCKADDR_H
+
+#ifdef LIBC_FULL_BUILD
+
+#include "include/llvm-libc-types/struct_sockaddr.h"
+
+#else
+
+#include <sys/socket.h>
+
+#endif // LIBC_FULL_BUILD
+
+#endif // LLVM_LIBC_HDR_TYPES_STRUCT_SOCKADDR_H

libc/include/CMakeLists.txt

@@ -593,6 +593,8 @@ add_header_macro(
     .llvm-libc-macros.sys_socket_macros
     .llvm-libc-types.sa_family_t
     .llvm-libc-types.socklen_t
+    .llvm-libc-types.struct_iovec
+    .llvm-libc-types.struct_msghdr
     .llvm-libc-types.struct_sockaddr
     .llvm-libc-types.struct_sockaddr_un
 )

libc/include/llvm-libc-types/CMakeLists.txt

@@ -117,8 +117,10 @@ add_header(
 add_header(wint_t HDR wint_t.h)
 add_header(sa_family_t HDR sa_family_t.h)
 add_header(socklen_t HDR socklen_t.h)
-add_header(struct_sockaddr_un HDR struct_sockaddr_un.h)
-add_header(struct_sockaddr HDR struct_sockaddr.h)
+add_header(struct_sockaddr_un HDR struct_sockaddr_un.h DEPENDS .sa_family_t)
+add_header(struct_sockaddr HDR struct_sockaddr.h DEPENDS .sa_family_t)
+add_header(struct_iovec HDR struct_iovec.h DEPENDS .size_t)
+add_header(struct_msghdr HDR struct_msghdr.h DEPENDS .size_t .socklen_t .struct_iovec)
 add_header(rpc_opcodes_t HDR rpc_opcodes_t.h)
 add_header(ACTION HDR ACTION.h)
 add_header(ENTRY HDR ENTRY.h)

libc/include/llvm-libc-types/struct_iovec.h

@@ -0,0 +1,19 @@
+//===-- Definition of struct iovec ----------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_TYPES_STRUCT_IOVEC_H
+#define LLVM_LIBC_TYPES_STRUCT_IOVEC_H
+
+#include "size_t.h"
+
+struct iovec {
+  void *iov_base;
+  size_t iov_len;
+};
+
+#endif // LLVM_LIBC_TYPES_STRUCT_IOVEC_H

libc/include/llvm-libc-types/struct_msghdr.h

@@ -0,0 +1,26 @@
+//===-- Definition of struct msghdr ---------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_TYPES_STRUCT_MSGHDR_H
+#define LLVM_LIBC_TYPES_STRUCT_MSGHDR_H
+
+#include "size_t.h"
+#include "socklen_t.h"
+#include "struct_iovec.h"
+
+struct msghdr {
+  void *msg_name;        /* Optional address */
+  socklen_t msg_namelen; /* Size of address */
+  struct iovec *msg_iov; /* Scatter/gather array */
+  size_t msg_iovlen;     /* # elements in msg_iov */
+  void *msg_control;     /* Ancillary data, see below */
+  size_t msg_controllen; /* Ancillary data buffer len */
+  int msg_flags;         /* Flags (unused) */
+};
+
+#endif // LLVM_LIBC_TYPES_STRUCT_MSGHDR_H

libc/newhdrgen/yaml/sys/socket.yaml

@@ -5,9 +5,21 @@ types:
   - type_name: struct_sockaddr
   - type_name: socklen_t
   - type_name: sa_family_t
+  - type_name: struct_msghdr
+  - type_name: struct_iovec
+  - type_name: size_t
+  - type_name: ssize_t
 enums: []
 objects: []
 functions:
+  - name: accept
+    standards:
+      - POSIX
+    return_type: int
+    arguments:
+      - type: int
+      - type: sockaddr *__restrict
+      - type: socklen_t *__restrict
   - name: bind
     standards:
       - POSIX
@@ -16,6 +28,77 @@ functions:
       - type: int
       - type: const struct sockaddr *
       - type: socklen_t
+  - name: connect
+    standards:
+      - POSIX
+    return_type: int
+    arguments:
+      - type: int
+      - type: const struct sockaddr *
+      - type: socklen_t
+  - name: listen
+    standards:
+      - POSIX
+    return_type: int
+    arguments:
+      - type: int
+      - type: int
+  - name: recv
+    standards:
+      - POSIX
+    return_type: ssize_t
+    arguments:
+      - type: int
+      - type: const void *
+      - type: size_t
+      - type: int
+  - name: recvfrom
+    standards:
+      - POSIX
+    return_type: ssize_t
+    arguments:
+      - type: int
+      - type: const void*
+      - type: size_t
+      - type: int
+      - type: const struct sockaddr *
+      - type: socklen_t
+  - name: recvmsg
+    standards:
+      - POSIX
+    return_type: ssize_t
+    arguments:
+      - type: int
+      - type: const struct msghdr *
+      - type: int
+  - name: send
+    standards:
+      - POSIX
+    return_type: ssize_t
+    arguments:
+      - type: int
+      - type: const void*
+      - type: size_t
+      - type: int
+  - name: sendmsg
+    standards:
+      - POSIX
+    return_type: ssize_t
+    arguments:
+      - type: int
+      - type: const struct msghdr *
+      - type: int
+  - name: sendto
+    standards:
+      - POSIX
+    return_type: ssize_t
+    arguments:
+      - type: int
+      - type: const void *
+      - type: size_t
+      - type: int
+      - type: const struct sockaddr *
+      - type: socklen_t
   - name: socket
     standards:
       - POSIX
@@ -24,3 +107,12 @@ functions:
       - type: int
       - type: int
       - type: int
+  - name: socketpair
+    standards:
+      - posix
+    return_type: int
+    arguments:
+      - type: int
+      - type: int
+      - type: int
+      - type: int*

libc/spec/posix.td

@@ -80,11 +80,20 @@ def GetoptArgvT : NamedType<"__getoptargv_t">;
 
 def SAFamilyType : NamedType<"sa_family_t">;
 def SocklenType : NamedType<"socklen_t">;
+def SocklenPtr : PtrType<SocklenType>;
 
 def StructSockAddr : NamedType<"struct sockaddr">;
 def StructSockAddrPtr : PtrType<StructSockAddr>;
 def ConstStructSockAddrPtr : ConstType<StructSockAddrPtr>;
 
+def StructMsghdr : NamedType<"struct msghdr">;
+def StructMsghdrPtr : PtrType<StructMsghdr>;
+def ConstStructMsghdrPtr : ConstType<StructMsghdrPtr>;
+
+def StructIovec : NamedType<"struct iovec">;
+def StructIovecPtr : PtrType<StructIovec>;
+def ConstStructIovecPtr : ConstType<StructIovecPtr>;
+
 def StructSockAddrUn : NamedType<"struct sockaddr_un">;
 
 def StructStatvfs : NamedType<"struct statvfs">;
@@ -1711,10 +1720,14 @@ def POSIX : StandardSpec<"POSIX"> {
         Macro<"SOCK_PACKET">,
       ], // Macros
       [
+        SizeTType,
+        SSizeTType,
         SAFamilyType,
         StructSockAddr,
         StructSockAddrUn,
         SocklenType,
+        StructIovec,
+        StructMsghdr,
       ], // Types
       [], // Enumerations
       [
@@ -1723,11 +1736,54 @@ def POSIX : StandardSpec<"POSIX"> {
           RetValSpec<IntType>,
           [ArgSpec<IntType>, ArgSpec<IntType>, ArgSpec<IntType>]
         >,
+        FunctionSpec<
+          "socketpair",
+          RetValSpec<IntType>,
+          [ArgSpec<IntType>, ArgSpec<IntType>, ArgSpec<IntType>, ArgSpec<IntPtr>]
+        >,
         FunctionSpec<
           "bind",
           RetValSpec<IntType>,
           [ArgSpec<IntType>, ArgSpec<ConstStructSockAddrPtr>, ArgSpec<SocklenType>]
         >,
+        FunctionSpec<
+          "send",
+          RetValSpec<SSizeTType>,
+          [ArgSpec<IntType>, ArgSpec<ConstVoidPtr>, ArgSpec<SizeTType>, ArgSpec<IntType>]
+        >,
+        FunctionSpec<
+          "sendto",
+          RetValSpec<SSizeTType>,
+          [
+            ArgSpec<IntType>, ArgSpec<ConstVoidPtr>, ArgSpec<SizeTType>,
+            ArgSpec<IntType>, ArgSpec<ConstStructSockAddrPtr>,
+            ArgSpec<SocklenType>
+          ]
+        >,
+        FunctionSpec<
+          "sendmsg",
+          RetValSpec<SSizeTType>,
+          [ArgSpec<IntType>, ArgSpec<ConstStructMsghdrPtr>, ArgSpec<IntType>]
+        >,
+        FunctionSpec<
+          "recv",
+          RetValSpec<SSizeTType>,
+          [ArgSpec<IntType>, ArgSpec<VoidPtr>, ArgSpec<SizeTType>, ArgSpec<IntType>]
+        >,
+        FunctionSpec<
+          "recvfrom",
+          RetValSpec<SSizeTType>,
+          [
+            ArgSpec<IntType>, ArgSpec<VoidPtr>, ArgSpec<SizeTType>,
+            ArgSpec<IntType>, ArgSpec<StructSockAddrPtr>,
+            ArgSpec<SocklenPtr>
+          ]
+        >,
+        FunctionSpec<
+          "recvmsg",
+          RetValSpec<SSizeTType>,
+          [ArgSpec<IntType>, ArgSpec<StructMsghdrPtr>, ArgSpec<IntType>]
+        >,
       ]  // Functions
   >;
 

libc/src/sys/socket/CMakeLists.txt

@@ -10,8 +10,50 @@ add_entrypoint_object(
 )
 
 add_entrypoint_object(
-  bind
+  socketpair
   ALIAS
   DEPENDS
-    .${LIBC_TARGET_OS}.bind
+    .${LIBC_TARGET_OS}.socketpair
+)
+
+add_entrypoint_object(
+  send
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.send
+)
+
+add_entrypoint_object(
+  sendto
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.sendto
+)
+
+add_entrypoint_object(
+  sendmsg
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.sendmsg
+)
+
+add_entrypoint_object(
+  recv
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.recv
+)
+
+add_entrypoint_object(
+  recvfrom
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.recvfrom
+)
+
+add_entrypoint_object(
+  recvmsg
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.recvmsg
 )

libc/src/sys/socket/linux/CMakeLists.txt

@@ -12,14 +12,95 @@ add_entrypoint_object(
 )
 
 add_entrypoint_object(
-  bind
+  socketpair
   SRCS
-    bind.cpp
+    socketpair.cpp
   HDRS
-    ../bind.h
+    ../socketpair.h
   DEPENDS
     libc.include.sys_syscall
     libc.include.sys_socket
     libc.src.__support.OSUtil.osutil
     libc.src.errno.errno
 )
+
+add_entrypoint_object(
+  send
+  SRCS
+    send.cpp
+  HDRS
+    ../send.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.hdr.types.struct_sockaddr
+    libc.hdr.types.socklen_t
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  sendto
+  SRCS
+    sendto.cpp
+  HDRS
+    ../sendto.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.hdr.types.struct_sockaddr
+    libc.hdr.types.socklen_t
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  sendmsg
+  SRCS
+    sendmsg.cpp
+  HDRS
+    ../sendmsg.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.hdr.types.struct_msghdr
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+add_entrypoint_object(
+  recv
+  SRCS
+    recv.cpp
+  HDRS
+    ../recv.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.hdr.types.struct_sockaddr
+    libc.hdr.types.socklen_t
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  recvfrom
+  SRCS
+    recvfrom.cpp
+  HDRS
+    ../recvfrom.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.hdr.types.struct_sockaddr
+    libc.hdr.types.socklen_t
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
+  recvmsg
+  SRCS
+    recvmsg.cpp
+  HDRS
+    ../recvmsg.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.hdr.types.struct_msghdr
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)

libc/src/sys/socket/linux/recv.cpp

@@ -0,0 +1,47 @@
+//===-- Linux implementation of recv --------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/sys/socket/recv.h"
+
+#include "hdr/types/socklen_t.h"
+#include "hdr/types/ssize_t.h"
+#include "hdr/types/struct_sockaddr.h"
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/errno/libc_errno.h"
+#include <linux/net.h>   // For SYS_SOCKET socketcall number.
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(ssize_t, recv,
+                   (int sockfd, const void *buf, size_t len, int flags)) {
+#ifdef SYS_recv
+  ssize_t ret =
+      LIBC_NAMESPACE::syscall_impl<int>(SYS_recv, sockfd, buf, len, flags);
+#elif defined(SYS_recvfrom)
+  ssize_t ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_recvfrom, sockfd,
+                                                  reinterpret_cast<long>(buf),
+                                                  len, flags, nullptr, 0);
+#elif defined(SYS_socketcall)
+  unsigned long sockcall_args[4] = {
+      static_cast<unsigned long>(sockfd), reinterpret_cast<unsigned long>(buf),
+      static_cast<unsigned long>(len), static_cast<unsigned long>(flags)};
+  ssize_t ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_socketcall, SYS_RECV,
+                                                  sockcall_args);
+#else
+#error "socket and socketcall syscalls unavailable for this platform."
+#endif
+  if (ret < 0) {
+    libc_errno = static_cast<int>(-ret);
+    return -1;
+  }
+  return ret;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/sys/socket/linux/recvfrom.cpp

@@ -0,0 +1,49 @@
+//===-- Linux implementation of recvfrom ----------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/sys/socket/recvfrom.h"
+
+#include "hdr/types/socklen_t.h"
+#include "hdr/types/ssize_t.h"
+#include "hdr/types/struct_sockaddr.h"
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/errno/libc_errno.h"
+#include <linux/net.h>   // For SYS_SOCKET socketcall number.
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(ssize_t, recvfrom,
+                   (int sockfd, const void *buf, size_t len, int flags,
+                    const struct sockaddr *dest_addr, socklen_t addrlen)) {
+#ifdef SYS_recvfrom
+
+  ssize_t ret = LIBC_NAMESPACE::syscall_impl<int>(
+      SYS_recvfrom, sockfd, reinterpret_cast<long>(buf), len, flags,
+      reinterpret_cast<long>(dest_addr), addrlen);
+#elif defined(SYS_socketcall)
+  unsigned long sockcall_args[6] = {static_cast<unsigned long>(sockfd),
+                                    reinterpret_cast<unsigned long>(buf),
+                                    static_cast<unsigned long>(len),
+                                    static_cast<unsigned long>(flags),
+                                    reinterpret_cast<unsigned long>(dest_addr),
+                                    static_cast<unsigned long>(addrlen)};
+  ssize_t ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_socketcall, SYS_RECVFROM,
+                                                  sockcall_args);
+#else
+#error "socket and socketcall syscalls unavailable for this platform."
+#endif
+  if (ret < 0) {
+    libc_errno = static_cast<int>(-ret);
+    return -1;
+  }
+  return ret;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/sys/socket/linux/recvmsg.cpp

@@ -0,0 +1,42 @@
+//===-- Linux implementation of recvmsg -----------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/sys/socket/recvmsg.h"
+
+#include "hdr/types/ssize_t.h"
+#include "hdr/types/struct_msghdr.h"
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/errno/libc_errno.h"
+#include <linux/net.h>   // For SYS_SOCKET socketcall number.
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(ssize_t, recvmsg,
+                   (int sockfd, const struct msghdr *msg, int flags)) {
+#ifdef SYS_recvmsg
+  ssize_t ret = LIBC_NAMESPACE::syscall_impl<int>(
+      SYS_recvmsg, sockfd, reinterpret_cast<long>(msg), flags);
+#elif defined(SYS_socketcall)
+  unsigned long sockcall_args[3] = {static_cast<unsigned long>(sockfd),
+                                    reinterpret_cast<unsigned long>(msg),
+                                    static_cast<unsigned long>(flags)};
+  ssize_t ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_socketcall, SYS_RECVMSG,
+                                                  sockcall_args);
+#else
+#error "socket and socketcall syscalls unavailable for this platform."
+#endif
+  if (ret < 0) {
+    libc_errno = static_cast<int>(-ret);
+    return -1;
+  }
+  return ret;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/sys/socket/linux/send.cpp

@@ -0,0 +1,46 @@
+//===-- Linux implementation of send --------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/sys/socket/send.h"
+
+#include "hdr/types/socklen_t.h"
+#include "hdr/types/ssize_t.h"
+#include "hdr/types/struct_sockaddr.h"
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/errno/libc_errno.h"
+#include <linux/net.h>   // For SYS_SOCKET socketcall number.
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(ssize_t, send,
+                   (int sockfd, const void *buf, size_t len, int flags)) {
+#ifdef SYS_send
+  ssize_t ret =
+      LIBC_NAMESPACE::syscall_impl<int>(SYS_send, sockfd, buf, len, flags);
+#elif defined(SYS_sendto)
+  ssize_t ret = LIBC_NAMESPACE::syscall_impl<int>(
+      SYS_sendto, sockfd, reinterpret_cast<long>(buf), len, flags, nullptr, 0);
+#elif defined(SYS_socketcall)
+  unsigned long sockcall_args[4] = {
+      static_cast<unsigned long>(sockfd), reinterpret_cast<unsigned long>(buf),
+      static_cast<unsigned long>(len), static_cast<unsigned long>(flags)};
+  ssize_t ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_socketcall, SYS_SEND,
+                                                  sockcall_args);
+#else
+#error "socket and socketcall syscalls unavailable for this platform."
+#endif
+  if (ret < 0) {
+    libc_errno = static_cast<int>(-ret);
+    return -1;
+  }
+  return ret;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/sys/socket/linux/sendmsg.cpp

@@ -0,0 +1,42 @@
+//===-- Linux implementation of sendmsg -----------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/sys/socket/sendmsg.h"
+
+#include "hdr/types/ssize_t.h"
+#include "hdr/types/struct_msghdr.h"
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/errno/libc_errno.h"
+#include <linux/net.h>   // For SYS_SOCKET socketcall number.
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(ssize_t, sendmsg,
+                   (int sockfd, const struct msghdr *msg, int flags)) {
+#ifdef SYS_sendmsg
+  ssize_t ret = LIBC_NAMESPACE::syscall_impl<int>(
+      SYS_sendmsg, sockfd, reinterpret_cast<long>(msg), flags);
+#elif defined(SYS_socketcall)
+  unsigned long sockcall_args[3] = {static_cast<unsigned long>(sockfd),
+                                    reinterpret_cast<unsigned long>(msg),
+                                    static_cast<unsigned long>(flags)};
+  ssize_t ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_socketcall, SYS_SENDMSG,
+                                                  sockcall_args);
+#else
+#error "socket and socketcall syscalls unavailable for this platform."
+#endif
+  if (ret < 0) {
+    libc_errno = static_cast<int>(-ret);
+    return -1;
+  }
+  return ret;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/sys/socket/linux/sendto.cpp

@@ -0,0 +1,49 @@
+//===-- Linux implementation of sendto ------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/sys/socket/sendto.h"
+
+#include "hdr/types/socklen_t.h"
+#include "hdr/types/ssize_t.h"
+#include "hdr/types/struct_sockaddr.h"
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+#include "src/errno/libc_errno.h"
+#include <linux/net.h>   // For SYS_SOCKET socketcall number.
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(ssize_t, sendto,
+                   (int sockfd, const void *buf, size_t len, int flags,
+                    const struct sockaddr *dest_addr, socklen_t addrlen)) {
+#ifdef SYS_sendto
+
+  ssize_t ret = LIBC_NAMESPACE::syscall_impl<int>(
+      SYS_sendto, sockfd, reinterpret_cast<long>(buf), len, flags,
+      reinterpret_cast<long>(dest_addr), addrlen);
+#elif defined(SYS_socketcall)
+  unsigned long sockcall_args[6] = {static_cast<unsigned long>(sockfd),
+                                    reinterpret_cast<unsigned long>(buf),
+                                    static_cast<unsigned long>(len),
+                                    static_cast<unsigned long>(flags),
+                                    reinterpret_cast<unsigned long>(dest_addr),
+                                    static_cast<unsigned long>(addrlen)};
+  ssize_t ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_socketcall, SYS_SENDTO,
+                                                  sockcall_args);
+#else
+#error "socket and socketcall syscalls unavailable for this platform."
+#endif
+  if (ret < 0) {
+    libc_errno = static_cast<int>(-ret);
+    return -1;
+  }
+  return ret;
+}
+
+} // namespace LIBC_NAMESPACE_DECL

libc/src/sys/socket/linux/socketpair.cpp

@@ -1,4 +1,4 @@
-//===-- Linux implementation of bind --------------------------------------===//
+//===-- Linux implementation of socketpair --------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "src/sys/socket/bind.h"
+#include "src/sys/socket/socketpair.h"
 
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
@@ -19,17 +19,16 @@
 
 namespace LIBC_NAMESPACE_DECL {
 
-LLVM_LIBC_FUNCTION(int, bind,
-                   (int domain, const struct sockaddr *address,
-                    socklen_t address_len)) {
-#ifdef SYS_socket
-  int ret =
-      LIBC_NAMESPACE::syscall_impl<int>(SYS_bind, domain, address, address_len);
+LLVM_LIBC_FUNCTION(int, socketpair,
+                   (int domain, int type, int protocol, int sv[2])) {
+#ifdef SYS_socketpair
+  int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_socketpair, domain, type,
+                                              protocol, sv);
 #elif defined(SYS_socketcall)
-  unsigned long sockcall_args[3] = {static_cast<unsigned long>(domain),
-                                    reinterpret_cast<unsigned long>(address),
-                                    static_cast<unsigned long>(address_len)};
-  int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_socketcall, SYS_BIND,
+  unsigned long sockcall_args[3] = {
+      static_cast<unsigned long>(domain), static_cast<unsigned long>(type),
+      static_cast<unsigned long>(protocol), static_cast<unsigned long>(sv)};
+  int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_socketcall, SYS_SOCKETPAIR,
                                               sockcall_args);
 #else
 #error "socket and socketcall syscalls unavailable for this platform."

libc/src/sys/socket/recv.h

@@ -1,4 +1,4 @@
-//===-- Implementation header for bind --------------------------*- C++ -*-===//
+//===-- Implementation header for recv --------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
@@ -6,16 +6,16 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef LLVM_LIBC_SRC_SYS_SOCKET_BIND_H
-#define LLVM_LIBC_SRC_SYS_SOCKET_BIND_H
+#ifndef LLVM_LIBC_SRC_SYS_SOCKET_RECV_H
+#define LLVM_LIBC_SRC_SYS_SOCKET_RECV_H
 
 #include "src/__support/macros/config.h"
 #include <sys/socket.h>
 
 namespace LIBC_NAMESPACE_DECL {
 
-int bind(int domain, const struct sockaddr *address, socklen_t address_len);
+ssize_t recv(int sockfd, const void *buf, size_t len, int flags);
 
 } // namespace LIBC_NAMESPACE_DECL
 
-#endif // LLVM_LIBC_SRC_SYS_SOCKET_BIND_H
+#endif // LLVM_LIBC_SRC_SYS_SOCKET_RECV_H

libc/src/sys/socket/recvfrom.h

@@ -0,0 +1,25 @@
+//===-- Implementation header for recvfrom ----------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_SYS_SOCKET_RECVFROM_H
+#define LLVM_LIBC_SRC_SYS_SOCKET_RECVFROM_H
+
+#include "hdr/types/socklen_t.h"
+#include "hdr/types/ssize_t.h"
+#include "hdr/types/struct_sockaddr.h"
+#include "src/__support/macros/config.h"
+#include <stddef.h> // For size_t
+
+namespace LIBC_NAMESPACE_DECL {
+
+ssize_t recvfrom(int sockfd, const void *buf, size_t len, int flags,
+                 const struct sockaddr *address, socklen_t addrlen);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SYS_SOCKET_RECVFROM_H

libc/src/sys/socket/recvmsg.h

@@ -0,0 +1,22 @@
+//===-- Implementation header for recvmsg -----------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_SYS_SOCKET_RECVMSG_H
+#define LLVM_LIBC_SRC_SYS_SOCKET_RECVMSG_H
+
+#include "hdr/types/ssize_t.h"
+#include "hdr/types/struct_msghdr.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+ssize_t recvmsg(int sockfd, const struct msghdr *msg, int flags);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SYS_SOCKET_RECVMSG_H

libc/src/sys/socket/send.h

@@ -0,0 +1,21 @@
+//===-- Implementation header for send --------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_SYS_SOCKET_SEND_H
+#define LLVM_LIBC_SRC_SYS_SOCKET_SEND_H
+
+#include "src/__support/macros/config.h"
+#include <sys/socket.h>
+
+namespace LIBC_NAMESPACE_DECL {
+
+ssize_t send(int sockfd, const void *buf, size_t len, int flags);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SYS_SOCKET_SEND_H

libc/src/sys/socket/sendmsg.h

@@ -0,0 +1,22 @@
+//===-- Implementation header for sendmsg -----------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_SYS_SOCKET_SENDMSG_H
+#define LLVM_LIBC_SRC_SYS_SOCKET_SENDMSG_H
+
+#include "hdr/types/ssize_t.h"
+#include "hdr/types/struct_msghdr.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+ssize_t sendmsg(int sockfd, const struct msghdr *msg, int flags);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SYS_SOCKET_SENDMSG_H

libc/src/sys/socket/sendto.h

@@ -0,0 +1,25 @@
+//===-- Implementation header for sendto ------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_SYS_SOCKET_SENDTO_H
+#define LLVM_LIBC_SRC_SYS_SOCKET_SENDTO_H
+
+#include "hdr/types/socklen_t.h"
+#include "hdr/types/ssize_t.h"
+#include "hdr/types/struct_sockaddr.h"
+#include "src/__support/macros/config.h"
+#include <stddef.h> // For size_t
+
+namespace LIBC_NAMESPACE_DECL {
+
+ssize_t sendto(int sockfd, const void *buf, size_t len, int flags,
+               const struct sockaddr *dest_addr, socklen_t addrlen);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SYS_SOCKET_SENDTO_H

libc/src/sys/socket/socketpair.h

@@ -0,0 +1,20 @@
+//===-- Implementation header for socketpair --------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_SYS_SOCKET_SOCKETPAIR_H
+#define LLVM_LIBC_SRC_SYS_SOCKET_SOCKETPAIR_H
+
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+int socketpair(int domain, int type, int protocol, int sv[2]);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_SYS_SOCKET_SOCKETPAIR_H

libc/test/src/sys/socket/linux/CMakeLists.txt

@@ -13,18 +13,60 @@ add_libc_unittest(
     libc.src.unistd.close
 )
 
-
 add_libc_unittest(
-  bind_test
+  socketpair_test
   SUITE
     libc_sys_socket_unittests
   SRCS
-    bind_test.cpp
+    socketpair_test.cpp
   DEPENDS
     libc.include.sys_socket
     libc.src.errno.errno
-    libc.src.sys.socket.socket
-    libc.src.sys.socket.bind
-    libc.src.stdio.remove
+    libc.src.sys.socket.socketpair
+    libc.src.unistd.close
+)
+
+add_libc_unittest(
+  send_recv_test
+  SUITE
+    libc_sys_socket_unittests
+  SRCS
+    send_recv_test.cpp
+  DEPENDS
+    libc.include.sys_socket
+    libc.src.errno.errno
+    libc.src.sys.socket.socketpair
+    libc.src.sys.socket.send
+    libc.src.sys.socket.recv
+    libc.src.unistd.close
+)
+
+add_libc_unittest(
+  sendto_recvfrom_test
+  SUITE
+    libc_sys_socket_unittests
+  SRCS
+    sendto_recvfrom_test.cpp
+  DEPENDS
+    libc.include.sys_socket
+    libc.src.errno.errno
+    libc.src.sys.socket.socketpair
+    libc.src.sys.socket.sendto
+    libc.src.sys.socket.recvfrom
+    libc.src.unistd.close
+)
+
+add_libc_unittest(
+  sendmsg_recvmsg_test
+  SUITE
+    libc_sys_socket_unittests
+  SRCS
+    sendmsg_recvmsg_test.cpp
+  DEPENDS
+    libc.include.sys_socket
+    libc.src.errno.errno
+    libc.src.sys.socket.socketpair
+    libc.src.sys.socket.sendmsg
+    libc.src.sys.socket.recvmsg
     libc.src.unistd.close
 )

libc/test/src/sys/socket/linux/bind_test.cpp

@@ -1,54 +0,0 @@
-//===-- Unittests for bind ------------------------------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#include "src/sys/socket/bind.h"
-#include "src/sys/socket/socket.h"
-
-#include "src/stdio/remove.h"
-#include "src/unistd/close.h"
-
-#include "src/errno/libc_errno.h"
-#include "test/UnitTest/Test.h"
-
-#include <sys/socket.h> // For AF_UNIX and SOCK_DGRAM
-
-TEST(LlvmLibcSocketTest, BindLocalSocket) {
-
-  const char *FILENAME = "bind_file.test";
-  auto SOCK_PATH = libc_make_test_file_path(FILENAME);
-
-  int sock = LIBC_NAMESPACE::socket(AF_UNIX, SOCK_DGRAM, 0);
-  ASSERT_GE(sock, 0);
-  ASSERT_ERRNO_SUCCESS();
-
-  struct sockaddr_un my_addr;
-
-  my_addr.sun_family = AF_UNIX;
-  unsigned int i = 0;
-  for (;
-       SOCK_PATH[i] != '\0' && (i < sizeof(sockaddr_un) - sizeof(sa_family_t));
-       ++i)
-    my_addr.sun_path[i] = SOCK_PATH[i];
-  my_addr.sun_path[i] = '\0';
-
-  // It's important that the path fits in the struct, if it doesn't then we
-  // can't try to bind to the file.
-  ASSERT_LT(
-      i, static_cast<unsigned int>(sizeof(sockaddr_un) - sizeof(sa_family_t)));
-
-  int result =
-      LIBC_NAMESPACE::bind(sock, reinterpret_cast<struct sockaddr *>(&my_addr),
-                           sizeof(struct sockaddr_un));
-
-  ASSERT_EQ(result, 0);
-  ASSERT_ERRNO_SUCCESS();
-
-  LIBC_NAMESPACE::close(sock);
-
-  LIBC_NAMESPACE::remove(SOCK_PATH);
-}

libc/test/src/sys/socket/linux/send_recv_test.cpp

@@ -0,0 +1,73 @@
+//===-- Unittests for send/recv -------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/sys/socket/recv.h"
+#include "src/sys/socket/send.h"
+#include "src/sys/socket/socketpair.h"
+
+#include "src/unistd/close.h"
+
+#include "src/errno/libc_errno.h"
+#include "test/UnitTest/Test.h"
+
+#include <sys/socket.h> // For AF_UNIX and SOCK_DGRAM
+
+TEST(LlvmLibcSendRecvTest, SucceedsWithSocketPair) {
+  const char TEST_MESSAGE[] = "connection successful";
+  const size_t MESSAGE_LEN = sizeof(TEST_MESSAGE);
+
+  int sockpair[2] = {0, 0};
+
+  int result = LIBC_NAMESPACE::socketpair(AF_UNIX, SOCK_STREAM, 0, sockpair);
+  ASSERT_EQ(result, 0);
+  ASSERT_ERRNO_SUCCESS();
+
+  ssize_t send_result =
+      LIBC_NAMESPACE::send(sockpair[0], TEST_MESSAGE, MESSAGE_LEN, 0);
+  EXPECT_EQ(send_result, static_cast<ssize_t>(MESSAGE_LEN));
+  ASSERT_ERRNO_SUCCESS();
+
+  char buffer[256];
+
+  ssize_t recv_result =
+      LIBC_NAMESPACE::recv(sockpair[1], buffer, sizeof(buffer), 0);
+  ASSERT_EQ(recv_result, static_cast<ssize_t>(MESSAGE_LEN));
+  ASSERT_ERRNO_SUCCESS();
+
+  ASSERT_STREQ(buffer, TEST_MESSAGE);
+
+  // close both ends of the socket
+  result = LIBC_NAMESPACE::close(sockpair[0]);
+  ASSERT_EQ(result, 0);
+  ASSERT_ERRNO_SUCCESS();
+
+  result = LIBC_NAMESPACE::close(sockpair[1]);
+  ASSERT_EQ(result, 0);
+  ASSERT_ERRNO_SUCCESS();
+}
+
+TEST(LlvmLibcSendRecvTest, SendFails) {
+  const char TEST_MESSAGE[] = "connection terminated";
+  const size_t MESSAGE_LEN = sizeof(TEST_MESSAGE);
+
+  ssize_t send_result = LIBC_NAMESPACE::send(-1, TEST_MESSAGE, MESSAGE_LEN, 0);
+  EXPECT_EQ(send_result, ssize_t(-1));
+  ASSERT_ERRNO_FAILURE();
+
+  LIBC_NAMESPACE::libc_errno = 0; // reset errno to avoid test ordering issues.
+}
+
+TEST(LlvmLibcSendRecvTest, RecvFails) {
+  char buffer[256];
+
+  ssize_t recv_result = LIBC_NAMESPACE::recv(-1, buffer, sizeof(buffer), 0);
+  ASSERT_EQ(recv_result, ssize_t(-1));
+  ASSERT_ERRNO_FAILURE();
+
+  LIBC_NAMESPACE::libc_errno = 0; // reset errno to avoid test ordering issues.
+}

libc/test/src/sys/socket/linux/sendmsg_recvmsg_test.cpp

@@ -0,0 +1,125 @@
+//===-- Unittests for sendmsg/recvmsg -------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/sys/socket/recvmsg.h"
+#include "src/sys/socket/sendmsg.h"
+#include "src/sys/socket/socketpair.h"
+
+#include "src/unistd/close.h"
+
+#include "src/errno/libc_errno.h"
+#include "test/UnitTest/Test.h"
+
+#include <sys/socket.h> // For AF_UNIX and SOCK_DGRAM
+
+TEST(LlvmLibcSendMsgRecvMsgTest, SucceedsWithSocketPair) {
+  const char TEST_MESSAGE[] = "connection successful";
+  const size_t MESSAGE_LEN = sizeof(TEST_MESSAGE);
+
+  int sockpair[2] = {0, 0};
+
+  int result = LIBC_NAMESPACE::socketpair(AF_UNIX, SOCK_STREAM, 0, sockpair);
+  ASSERT_EQ(result, 0);
+  ASSERT_ERRNO_SUCCESS();
+
+  iovec send_msg_text;
+  send_msg_text.iov_base =
+      reinterpret_cast<void *>(const_cast<char *>(TEST_MESSAGE));
+  send_msg_text.iov_len = MESSAGE_LEN;
+
+  msghdr send_message;
+  send_message.msg_name = nullptr;
+  send_message.msg_namelen = 0;
+  send_message.msg_iov = &send_msg_text;
+  send_message.msg_iovlen = 1;
+  send_message.msg_control = nullptr;
+  send_message.msg_controllen = 0;
+  send_message.msg_flags = 0;
+
+  ssize_t send_result = LIBC_NAMESPACE::sendmsg(sockpair[0], &send_message, 0);
+  EXPECT_EQ(send_result, static_cast<ssize_t>(MESSAGE_LEN));
+  ASSERT_ERRNO_SUCCESS();
+
+  char buffer[256];
+
+  iovec recv_msg_text;
+  recv_msg_text.iov_base = reinterpret_cast<void *>(buffer);
+  recv_msg_text.iov_len = sizeof(buffer);
+
+  msghdr recv_message;
+  recv_message.msg_name = nullptr;
+  recv_message.msg_namelen = 0;
+  recv_message.msg_iov = &recv_msg_text;
+  recv_message.msg_iovlen = 1;
+  recv_message.msg_control = nullptr;
+  recv_message.msg_controllen = 0;
+  recv_message.msg_flags = 0;
+
+  ssize_t recv_result = LIBC_NAMESPACE::recvmsg(sockpair[1], &recv_message, 0);
+  ASSERT_EQ(recv_result, static_cast<ssize_t>(MESSAGE_LEN));
+  ASSERT_ERRNO_SUCCESS();
+
+  ASSERT_STREQ(buffer, TEST_MESSAGE);
+
+  // close both ends of the socket
+  result = LIBC_NAMESPACE::close(sockpair[0]);
+  ASSERT_EQ(result, 0);
+  ASSERT_ERRNO_SUCCESS();
+
+  result = LIBC_NAMESPACE::close(sockpair[1]);
+  ASSERT_EQ(result, 0);
+  ASSERT_ERRNO_SUCCESS();
+}
+
+TEST(LlvmLibcSendMsgRecvMsgTest, SendFails) {
+  const char TEST_MESSAGE[] = "connection terminated";
+  const size_t MESSAGE_LEN = sizeof(TEST_MESSAGE);
+
+  iovec send_msg_text;
+  send_msg_text.iov_base =
+      reinterpret_cast<void *>(const_cast<char *>(TEST_MESSAGE));
+  send_msg_text.iov_len = MESSAGE_LEN;
+
+  msghdr send_message;
+  send_message.msg_name = nullptr;
+  send_message.msg_namelen = 0;
+  send_message.msg_iov = &send_msg_text;
+  send_message.msg_iovlen = 1;
+  send_message.msg_control = nullptr;
+  send_message.msg_controllen = 0;
+  send_message.msg_flags = 0;
+
+  ssize_t send_result = LIBC_NAMESPACE::sendmsg(-1, &send_message, 0);
+  EXPECT_EQ(send_result, ssize_t(-1));
+  ASSERT_ERRNO_FAILURE();
+
+  LIBC_NAMESPACE::libc_errno = 0; // reset errno to avoid test ordering issues.
+}
+
+TEST(LlvmLibcSendMsgRecvMsgTest, RecvFails) {
+  char buffer[256];
+
+  iovec recv_msg_text;
+  recv_msg_text.iov_base = reinterpret_cast<void *>(buffer);
+  recv_msg_text.iov_len = sizeof(buffer);
+
+  msghdr recv_message;
+  recv_message.msg_name = nullptr;
+  recv_message.msg_namelen = 0;
+  recv_message.msg_iov = &recv_msg_text;
+  recv_message.msg_iovlen = 1;
+  recv_message.msg_control = nullptr;
+  recv_message.msg_controllen = 0;
+  recv_message.msg_flags = 0;
+
+  ssize_t recv_result = LIBC_NAMESPACE::recvmsg(-1, &recv_message, 0);
+  ASSERT_EQ(recv_result, ssize_t(-1));
+  ASSERT_ERRNO_FAILURE();
+
+  LIBC_NAMESPACE::libc_errno = 0; // reset errno to avoid test ordering issues.
+}

libc/test/src/sys/socket/linux/sendto_recvfrom_test.cpp

@@ -0,0 +1,75 @@
+//===-- Unittests for sendto/recvfrom -------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/sys/socket/recvfrom.h"
+#include "src/sys/socket/sendto.h"
+#include "src/sys/socket/socketpair.h"
+
+#include "src/unistd/close.h"
+
+#include "src/errno/libc_errno.h"
+#include "test/UnitTest/Test.h"
+
+#include <sys/socket.h> // For AF_UNIX and SOCK_DGRAM
+
+TEST(LlvmLibcSendToRecvFromTest, SucceedsWithSocketPair) {
+  const char TEST_MESSAGE[] = "connection successful";
+  const size_t MESSAGE_LEN = sizeof(TEST_MESSAGE);
+
+  int sockpair[2] = {0, 0};
+
+  int result = LIBC_NAMESPACE::socketpair(AF_UNIX, SOCK_STREAM, 0, sockpair);
+  ASSERT_EQ(result, 0);
+  ASSERT_ERRNO_SUCCESS();
+
+  ssize_t send_result = LIBC_NAMESPACE::sendto(sockpair[0], TEST_MESSAGE,
+                                               MESSAGE_LEN, 0, nullptr, 0);
+  EXPECT_EQ(send_result, static_cast<ssize_t>(MESSAGE_LEN));
+  ASSERT_ERRNO_SUCCESS();
+
+  char buffer[256];
+
+  ssize_t recv_result = LIBC_NAMESPACE::recvfrom(sockpair[1], buffer,
+                                                 sizeof(buffer), 0, nullptr, 0);
+  ASSERT_EQ(recv_result, static_cast<ssize_t>(MESSAGE_LEN));
+  ASSERT_ERRNO_SUCCESS();
+
+  ASSERT_STREQ(buffer, TEST_MESSAGE);
+
+  // close both ends of the socket
+  result = LIBC_NAMESPACE::close(sockpair[0]);
+  ASSERT_EQ(result, 0);
+  ASSERT_ERRNO_SUCCESS();
+
+  result = LIBC_NAMESPACE::close(sockpair[1]);
+  ASSERT_EQ(result, 0);
+  ASSERT_ERRNO_SUCCESS();
+}
+
+TEST(LlvmLibcSendToRecvFromTest, SendToFails) {
+  const char TEST_MESSAGE[] = "connection terminated";
+  const size_t MESSAGE_LEN = sizeof(TEST_MESSAGE);
+
+  ssize_t send_result =
+      LIBC_NAMESPACE::sendto(-1, TEST_MESSAGE, MESSAGE_LEN, 0, nullptr, 0);
+  EXPECT_EQ(send_result, ssize_t(-1));
+  ASSERT_ERRNO_FAILURE();
+
+  LIBC_NAMESPACE::libc_errno = 0; // reset errno to avoid test ordering issues.
+}
+
+TEST(LlvmLibcSendToRecvFromTest, RecvFromFails) {
+  char buffer[256];
+
+  ssize_t recv_result =
+      LIBC_NAMESPACE::recvfrom(-1, buffer, sizeof(buffer), 0, nullptr, 0);
+  ASSERT_EQ(recv_result, ssize_t(-1));
+  ASSERT_ERRNO_FAILURE();
+
+  LIBC_NAMESPACE::libc_errno = 0; // reset errno to avoid test ordering issues.
+}

libc/test/src/sys/socket/linux/socketpair_test.cpp

@@ -0,0 +1,37 @@
+//===-- Unittests for socketpair ------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/sys/socket/socketpair.h"
+
+#include "src/unistd/close.h"
+
+#include "src/errno/libc_errno.h"
+#include "test/UnitTest/Test.h"
+
+#include <sys/socket.h> // For AF_UNIX and SOCK_DGRAM
+
+TEST(LlvmLibcSocketPairTest, LocalSocket) {
+  int sockpair[2] = {-1, -1};
+  int result = LIBC_NAMESPACE::socketpair(AF_UNIX, SOCK_DGRAM, 0, sockpair);
+  ASSERT_EQ(result, 0);
+  ASSERT_ERRNO_SUCCESS();
+
+  ASSERT_GE(sockpair[0], 0);
+  ASSERT_GE(sockpair[1], 0);
+
+  LIBC_NAMESPACE::close(sockpair[0]);
+  LIBC_NAMESPACE::close(sockpair[1]);
+  ASSERT_ERRNO_SUCCESS();
+}
+
+TEST(LlvmLibcSocketPairTest, SocketFails) {
+  int sockpair[2] = {-1, -1};
+  int result = LIBC_NAMESPACE::socketpair(-1, -1, -1, sockpair);
+  ASSERT_EQ(result, -1);
+  ASSERT_ERRNO_FAILURE();
+}

utils/bazel/llvm-project-overlay/libc/BUILD.bazel

@@ -217,6 +217,26 @@ libc_support_library(
     hdrs = ["hdr/types/FILE.h"],
 )
 
+libc_support_library(
+    name = "types_ssize_t",
+    hdrs = ["hdr/types/ssize_t.h"],
+)
+
+libc_support_library(
+    name = "types_socklen_t",
+    hdrs = ["hdr/types/socklen_t.h"],
+)
+
+libc_support_library(
+    name = "types_struct_sockaddr",
+    hdrs = ["hdr/types/struct_sockaddr.h"],
+)
+
+libc_support_library(
+    name = "types_struct_msghdr",
+    hdrs = ["hdr/types/struct_msghdr.h"],
+)
+
 ############################### Support libraries ##############################
 
 libc_support_library(
@@ -4153,6 +4173,112 @@ libc_function(
     ],
 )
 
+############################## sys/socket targets ##############################
+
+libc_function(
+    name = "socket",
+    srcs = ["src/sys/socket/linux/socket.cpp"],
+    hdrs = ["src/sys/socket/socket.h"],
+    deps = [
+        ":__support_common",
+        ":__support_osutil_syscall",
+        ":errno",
+    ],
+)
+
+libc_function(
+    name = "socketpair",
+    srcs = ["src/sys/socket/linux/socketpair.cpp"],
+    hdrs = ["src/sys/socket/socketpair.h"],
+    deps = [
+        ":__support_common",
+        ":__support_osutil_syscall",
+        ":errno",
+    ],
+)
+
+libc_function(
+    name = "send",
+    srcs = ["src/sys/socket/linux/send.cpp"],
+    hdrs = ["src/sys/socket/send.h"],
+    deps = [
+        ":__support_common",
+        ":__support_osutil_syscall",
+        ":errno",
+        ":types_socklen_t",
+        ":types_ssize_t",
+        ":types_struct_sockaddr",
+    ],
+)
+
+libc_function(
+    name = "sendto",
+    srcs = ["src/sys/socket/linux/sendto.cpp"],
+    hdrs = ["src/sys/socket/sendto.h"],
+    deps = [
+        ":__support_common",
+        ":__support_osutil_syscall",
+        ":errno",
+        ":types_socklen_t",
+        ":types_ssize_t",
+        ":types_struct_sockaddr",
+    ],
+)
+
+libc_function(
+    name = "sendmsg",
+    srcs = ["src/sys/socket/linux/sendmsg.cpp"],
+    hdrs = ["src/sys/socket/sendmsg.h"],
+    deps = [
+        ":__support_common",
+        ":__support_osutil_syscall",
+        ":errno",
+        ":types_ssize_t",
+        ":types_struct_msghdr",
+    ],
+)
+
+libc_function(
+    name = "recv",
+    srcs = ["src/sys/socket/linux/recv.cpp"],
+    hdrs = ["src/sys/socket/recv.h"],
+    deps = [
+        ":__support_common",
+        ":__support_osutil_syscall",
+        ":errno",
+        ":types_socklen_t",
+        ":types_ssize_t",
+        ":types_struct_sockaddr",
+    ],
+)
+
+libc_function(
+    name = "recvfrom",
+    srcs = ["src/sys/socket/linux/recvfrom.cpp"],
+    hdrs = ["src/sys/socket/recvfrom.h"],
+    deps = [
+        ":__support_common",
+        ":__support_osutil_syscall",
+        ":errno",
+        ":types_socklen_t",
+        ":types_ssize_t",
+        ":types_struct_sockaddr",
+    ],
+)
+
+libc_function(
+    name = "recvmsg",
+    srcs = ["src/sys/socket/linux/recvmsg.cpp"],
+    hdrs = ["src/sys/socket/recvmsg.h"],
+    deps = [
+        ":__support_common",
+        ":__support_osutil_syscall",
+        ":errno",
+        ":types_ssize_t",
+        ":types_struct_msghdr",
+    ],
+)
+
 ############################## sys/epoll targets ###############################
 
 libc_function(

utils/bazel/llvm-project-overlay/libc/test/src/sys/socket/BUILD.bazel

@@ -0,0 +1,62 @@
+# This file is licensed under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+# Tests for LLVM libc string.h functions.
+
+load("//libc/test:libc_test_rules.bzl", "libc_test")
+
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])
+
+libc_test(
+    name = "socket_test",
+    srcs = ["linux/socket_test.cpp"],
+    libc_function_deps = [
+        "//libc:socket",
+        "//libc:close",
+    ],
+)
+
+libc_test(
+    name = "socketpair_test",
+    srcs = ["linux/socketpair_test.cpp"],
+    libc_function_deps = [
+        "//libc:socketpair",
+        "//libc:close",
+    ],
+)
+
+libc_test(
+    name = "send_recv_test",
+    srcs = ["linux/send_recv_test.cpp"],
+    libc_function_deps = [
+        "//libc:socketpair",
+        "//libc:send",
+        "//libc:recv",
+        "//libc:close",
+    ],
+)
+
+libc_test(
+    name = "sendto_recvfrom_test",
+    srcs = ["linux/sendto_recvfrom_test.cpp"],
+    libc_function_deps = [
+        "//libc:socketpair",
+        "//libc:sendto",
+        "//libc:recvfrom",
+        "//libc:close",
+    ],
+)
+
+libc_test(
+    name = "sendmsg_recvmsg_test",
+    srcs = ["linux/sendmsg_recvmsg_test.cpp"],
+    libc_function_deps = [
+        "//libc:socketpair",
+        "//libc:sendmsg",
+        "//libc:recvmsg",
+        "//libc:close",
+    ],
+)