socket: use accept4/paccept for nonblocking socket

This reduces the no. of syscalls on Linux systems from 2, accept(2) and
fcntl(2) for setting O_NONBLOCK, to a single accept4(2).  On NetBSD, we
have paccept(2) that does the same, if we leave signal masking aside.

Added sys_accept which accepts an extra flags argument than accept(2).
This would opportunistically use accept4/paccept as available.  It would
fallback to accept(2) and fcntl(2) otherwise.

While at this, the patch sets FD_CLOEXEC flag on the accepted socket fd.

BUG: 1236272
Change-Id: I41e43fd3e36d6dabb07e578a1cea7f45b7b4e37f
fixes: bz#1236272
Signed-off-by: Krishnan Parthasarathi <kparthas@redhat.com>

3 files changed, 65 insertions, 0 deletions

diff --git a/libglusterfs/src/libglusterfs.sym b/libglusterfs/src/libglusterfs.sym
index 18c9fff34a2..27eb1175b56 100644
--- a/libglusterfs/src/libglusterfs.sym
+++ b/libglusterfs/src/libglusterfs.sym
@@ -1052,6 +1052,7 @@ sys_utimensat
 sys_write
 sys_writev
 sys_socket
+sys_accept
 tbf_init
 tbf_throttle
 timespec_now
diff --git a/libglusterfs/src/syscall.c b/libglusterfs/src/syscall.c
index dd504f734fc..b28f2b9d17d 100644
--- a/libglusterfs/src/syscall.c
+++ b/libglusterfs/src/syscall.c
@@ -741,3 +741,63 @@ sys_socket(int domain, int type, int protocol)
         fcntl(fd, F_SETFD, FD_CLOEXEC);
     return fd;
 }
+
+#if (defined(HAVE_ACCEPT4) || defined(HAVE_PACCEPT))
+static inline int
+prep_accept_flags(int flags)
+{
+    if (flags & O_NONBLOCK) {
+        flags &= ~O_NONBLOCK;
+        flags |= SOCK_NONBLOCK;
+    }
+
+    flags |= SOCK_CLOEXEC;
+
+    return flags;
+}
+#endif
+
+int
+sys_accept(int sock, struct sockaddr *sockaddr, socklen_t *socklen, int flags)
+{
+    int newsock = -1;
+
+#ifdef HAVE_ACCEPT4
+
+    flags = prep_accept_flags(flags);
+    newsock = accept4(sock, sockaddr, socklen, flags);
+
+#elif HAVE_PACCEPT
+    flags = prep_accept_flags(flags);
+    newsock = paccept(sock, sockaddr, socklen, NULL, flags);
+
+#else
+    int op_errno = 0;
+    int curflag = 0;
+    int ret = 0;
+
+    newsock = accept(sock, sockaddr, socklen);
+    if (newsock != -1) {
+        curflag = fcntl(newsock, F_GETFL);
+        if (fcntl(newsock, F_SETFL, curflag | flags) == -1) {
+            op_errno = errno;
+            goto err;
+        }
+
+        curflag = fcntl(newsock, F_GETFD);
+        if (fcntl(newsock, F_SETFD, curflag | FD_CLOEXEC) == -1) {
+            op_errno = errno;
+            goto err;
+        }
+    }
+
+err:
+    if (op_errno) {
+        close(newsock);
+        errno = op_errno;
+        return -1;
+    }
+
+#endif
+    return newsock;
+}
diff --git a/libglusterfs/src/syscall.h b/libglusterfs/src/syscall.h
index 9bad49edb7c..faaf694b22c 100644
--- a/libglusterfs/src/syscall.h
+++ b/libglusterfs/src/syscall.h
@@ -16,6 +16,7 @@
 #include <sys/statvfs.h>
 #include <sys/stat.h>
 #include <sys/time.h>
+#include <sys/socket.h>
 
 /* GF follows the Linux XATTR definition, which differs in Darwin. */
 #define GF_XATTR_CREATE 0x1  /* set value, fail if attr already exists */
@@ -224,4 +225,7 @@ sys_pwrite(int fd, const void *buf, size_t count, off_t offset);
 int
 sys_socket(int domain, int type, int protocol);
 
+int
+sys_accept(int sock, struct sockaddr *sockaddr, socklen_t *socklen, int flags);
+
 #endif /* __SYSCALL_H__ */