[libc] add socket function

[michaelrj]

Summary

This patch adds the function "socket" from the header "sys/socket". It's
a simple syscall wrapper, and I plan on adding the related functions in
a followup patch.

[sivachandra]

LGTM but I have left a few minor comments.

libc/include/llvm-libc-macros/linux/sys-socket-macros.h

26

Can add some documentation about the origin of these numbers?

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

16

Same here - documentation for why 14.

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

16

For SYS_SOCKET socketcall call number. ?

[michaelrj]

libc/include/llvm-libc-macros/linux/sys-socket-macros.h

26

The source is the same as the above numbers, so I figured it was covered by the comment at the top of the file.

[michaelrj]

address comments and fix how types are set up.

[michaelrj]

fix issues that came up in testing before landing

libc/config/linux/x86_64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
 
     # sys/resource.h entrypoints
     libc.src.sys.resource.getrlimit
     libc.src.sys.resource.setrlimit
 
     # sys/sendfile entrypoints
     libc.src.sys.sendfile.sendfile
 
+    # sys/socket.h entrypoints
+    libc.src.sys.socket.socket
+
     # sys/stat.h entrypoints
     libc.src.sys.stat.chmod
     libc.src.sys.stat.fchmod
     libc.src.sys.stat.fchmodat
     libc.src.sys.stat.fstat
     libc.src.sys.stat.lstat
     libc.src.sys.stat.mkdir
     libc.src.sys.stat.mkdirat

libc/include/llvm-libc-macros/linux/sys-socket-macros.h

 // Macro values come from the Linux syscall interface.
 
 #define AF_UNSPEC 0 // Unspecified
 #define AF_UNIX 1   // Unix domain sockets
 #define AF_LOCAL 1  // POSIX name for AF_UNIX
 #define AF_INET 2   // Internet IPv4 Protocol
 #define AF_INET6 10 // IP version 6
 
+#define SOCK_STREAM 1
+#define SOCK_DGRAM 2
+#define SOCK_RAW 3
+#define SOCK_RDM 4
+#define SOCK_SEQPACKET 5
+#define SOCK_PACKET 10
+
 #endif // __LLVM_LIBC_MACROS_LINUX_SYS_SOCKET_MACROS_H

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

+//===-- Definition of sa_family_t type ------------------------------------===//
+//
+// 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_SA_FAMILY_T_H__
+#define __LLVM_LIBC_TYPES_SA_FAMILY_T_H__
+
+// The posix standard only says of sa_family_t that it must be unsigned. The
+// linux man page for "address_families" lists approximately 32 different
+// address families, meaning that a short 16 bit number will have plenty of
+// space for all of them.
+
+typedef unsigned short sa_family_t;
+
+#endif // __LLVM_LIBC_TYPES_SA_FAMILY_T_H__

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

+//===-- Definition of struct stat -----------------------------------------===//
+//
+// 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_STAT_H__
+#define __LLVM_LIBC_TYPES_STRUCT_STAT_H__
+
+#include <llvm-libc-types/sa_family_t.h>
+
+struct sockaddr {
+  sa_family_t sa_family;
+  char sa_data[14];
+}
+
+#endif // __LLVM_LIBC_TYPES_STRUCT_STAT_H__

libc/src/sys/CMakeLists.txt

 add_subdirectory(mman)
 add_subdirectory(random)
 add_subdirectory(resource)
 add_subdirectory(select)
+add_subdirectory(socket)
 add_subdirectory(sendfile)
 add_subdirectory(stat)
 add_subdirectory(utsname)
 add_subdirectory(wait)

libc/src/sys/socket/CMakeLists.txt

+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+  add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+endif()
+
+add_entrypoint_object(
+  socket
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.socket
+)
+

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

+add_entrypoint_object(
+  socket
+  SRCS
+    socket.cpp
+  HDRS
+    ../socket.h
+  DEPENDS
+    libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)

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

+//===-- Linux implementation of socket ------------------------------------===//
+//
+// 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/socket.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 socketcall numbers.
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(int, socket, (int domain, int type, int protocol)) {
+#ifdef SYS_socket
+  long ret = __llvm_libc::syscall_impl(SYS_socket, domain, type, protocol);
+#elif defined(SYS_socketcall)
+  unsigned long sockcall_args[3] = {domain, type, protocol};
+  long ret =
+      __llvm_libc::syscall_impl(SYS_socketcall, SYS_SOCKET, sockcall_args);
+#else
+#error "socket and socketcall syscalls unavailable for this platform."
+#endif
+  if (ret < 0) {
+    libc_errno = -ret;
+    return -1;
+  }
+  return ret;
+}
+
+} // namespace __llvm_libc

libc/src/sys/socket/socket.h

+//===-- Implementation header for socket ------------------------*- 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_SENDFILE_H
+#define LLVM_LIBC_SRC_SYS_SOCKET_SENDFILE_H
+
+namespace __llvm_libc {
+
+int socket(int domain, int type, int protocol);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SYS_SOCKET_SENDFILE_H

libc/test/src/sys/CMakeLists.txt

 add_subdirectory(mman)
 add_subdirectory(random)
 add_subdirectory(resource)
 add_subdirectory(select)
 add_subdirectory(sendfile)
+add_subdirectory(socket)
 add_subdirectory(stat)
 add_subdirectory(utsname)
 add_subdirectory(wait)

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

+if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_OS})
+  add_subdirectory(${LIBC_TARGET_OS})
+endif()

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

+add_custom_target(libc_sys_socket_unittests)
+
+add_libc_unittest(
+  socket_test
+  SUITE
+    libc_sys_socket_unittests
+  SRCS
+    socket_test.cpp
+  DEPENDS
+    libc.include.sys_socket
+    libc.src.errno.errno
+    libc.src.sys.socket.socket
+    libc.src.unistd.close
+)

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

+//===-- Unittests for socket ----------------------------------------------===//
+//
+// 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/socket.h"
+
+#include "src/unistd/close.h"
+
+#include "src/errno/libc_errno.h"
+#include "test/UnitTest/Test.h"
+
+#include <sys/socket.h> // For AF_LOCAL and SOCK_DGRAM
+
+TEST(LlvmLibcSocketTest, LocalSocket) {
+  int sock = __llvm_libc::socket(AF_LOCAL, SOCK_DGRAM, 0);
+  ASSERT_GE(sock, 0);
+  ASSERT_EQ(libc_errno, 0);
+
+  __llvm_libc::close(sock);
+}