From f876667cc562061bd5c9646aa20302d5be1a35c7 Mon Sep 17 00:00:00 2001
From: Jonas 'Sortie' Termansen <sortie@maxsi.org>
Date: Mon, 18 Jan 2016 14:43:49 +0100
Subject: [PATCH] Add socketpair(2) AF_UNIX stream support.

---
 libc/sys/socket/socketpair.cpp | 124 +++++++++++++++++++++++++++++++--
 1 file changed, 119 insertions(+), 5 deletions(-)

diff --git a/libc/sys/socket/socketpair.cpp b/libc/sys/socket/socketpair.cpp
index 80ca0c4f..73a474fb 100644
--- a/libc/sys/socket/socketpair.cpp
+++ b/libc/sys/socket/socketpair.cpp
@@ -1,6 +1,6 @@
 /*******************************************************************************
 
-    Copyright(C) Jonas 'Sortie' Termansen 2013.
+    Copyright(C) Jonas 'Sortie' Termansen 2016.
 
     This file is part of the Sortix C Library.
 
@@ -23,12 +23,126 @@
 *******************************************************************************/
 
 #include <sys/socket.h>
+#include <sys/un.h>
 
 #include <errno.h>
-#include <stdio.h>
+#include <fcntl.h>
+#include <pthread.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
 
-extern "C" int socketpair(int, int, int, int[2])
+#define FLAGS_MASK (SOCK_NONBLOCK | SOCK_CLOEXEC | SOCK_CLOFORK)
+#define TYPE_MASK (~FLAGS_MASK)
+#define FLAGS(x) ((x) & FLAGS_MASK)
+#define TYPE(x) ((x) & TYPE_MASK)
+
+static char randchar(void)
 {
-	fprintf(stderr, "%s is not implemented yet.\n", __func__);
-	return errno = ENOSYS, -1;
+	int index = arc4random_uniform(26 + 26 + 10);
+	if ( index < 26 )
+		return 'a' + index;
+	if ( index < 26 + 26 )
+		return 'A' + (index - 26);
+	return '0' + (index - (26 + 26));
+}
+
+struct accept_thread
+{
+	int listen_fd;
+	int fd;
+	int flags;
+	int errnum;
+};
+
+static void* accept_thread(void* arg_ptr)
+{
+	struct accept_thread* arg = (struct accept_thread*) arg_ptr;
+	arg->fd = accept4(arg->listen_fd, NULL, NULL, arg->flags);
+	arg->errnum = errno;
+	return NULL;
+}
+
+static int socketpair_unix_stream(int flags, int fds[2])
+{
+	char templ[] = "/tmp/socketpair.XXXXXXXXXX";
+	size_t templ_len = strlen(templ);
+	while ( true )
+	{
+		for ( size_t i = 0; i < 10; i++ )
+			templ[templ_len - i] = randchar();
+		int listen_flags = SOCK_CLOEXEC | SOCK_CLOFORK;
+		int listen_fd = socket(AF_UNIX, SOCK_STREAM | listen_flags, 0);
+		if ( listen_fd < 0 )
+			return -1;
+		struct sockaddr_un addr;
+		memset(&addr, 0, sizeof(addr));
+		addr.sun_family = AF_UNIX;
+		memcpy(addr.sun_path, templ, templ_len + 1);
+		if ( bind(listen_fd, (struct sockaddr*) &addr, sizeof(addr)) < 0 )
+			return -1;
+		if ( listen(listen_fd, 1) < 0 )
+		{
+			if ( errno == EADDRINUSE )
+				continue;
+			close(listen_fd);
+			return -1;
+		}
+		int client_flags = flags & ~SOCK_NONBLOCK;
+		int client_fd = socket(AF_UNIX, SOCK_STREAM | client_flags, 0);
+		if ( client_fd < 0 )
+		{
+			int errnum = errno;
+			close(listen_fd);
+			unlink(templ);
+			return errno = errnum, -1;
+		}
+		struct accept_thread arg;
+		arg.listen_fd = listen_fd;
+		arg.flags = flags;
+		pthread_attr_t thread_attr;
+		pthread_attr_init(&thread_attr);
+		pthread_attr_setstacksize(&thread_attr, 8192);
+		pthread_t thread;
+		int ret = pthread_create(&thread, &thread_attr, accept_thread, &arg);
+		pthread_attr_destroy(&thread_attr);
+		if ( ret != 0 )
+		{
+			close(listen_fd);
+			close(client_fd);
+			unlink(templ);
+			return errno = ret, -1;
+		}
+		ret = connect(client_fd, (struct sockaddr*) &addr, sizeof(addr));
+		pthread_join(thread, NULL);
+		if ( ret < 0 )
+		{
+			int errnum = errno;
+			close(listen_fd);
+			close(client_fd);
+			unlink(templ);
+			return errno = errnum, -1;
+		}
+		close(listen_fd);
+		unlink(templ);
+		if ( flags & SOCK_NONBLOCK )
+			fcntl(client_fd, F_SETFL, flags);
+		fds[0] = client_fd;
+		fds[1] = arg.fd;
+		return 0;
+	}
+}
+
+extern "C" int socketpair(int family, int type, int protocol, int fds[2])
+{
+	if ( family == AF_UNIX )
+	{
+		if ( protocol != 0 )
+			return errno = EPROTONOSUPPORT, -1;
+		if ( TYPE(type) == SOCK_STREAM )
+			return socketpair_unix_stream(FLAGS(type), fds);
+		else
+			return errno = EPROTOTYPE, -1;
+	}
+	return errno = EAFNOSUPPORT, -1;
 }