flag parameters: NONBLOCK in socket and socketpair
This patch introduces support for the SOCK_NONBLOCK flag in socket,
socketpair, and paccept. To do this the internal function sock_attach_fd
gets an additional parameter which it uses to set the appropriate flag for
the file descriptor.
Given that in modern, scalable programs almost all socket connections are
non-blocking and the minimal additional cost for the new functionality
I see no reason not to add this code.
The following test must be adjusted for architectures other than x86 and
x86-64 and in case the syscall numbers changed.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#include <fcntl.h>
#include <pthread.h>
#include <stdio.h>
#include <unistd.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/syscall.h>
#ifndef __NR_paccept
# ifdef __x86_64__
# define __NR_paccept 288
# elif defined __i386__
# define SYS_PACCEPT 18
# define USE_SOCKETCALL 1
# else
# error "need __NR_paccept"
# endif
#endif
#ifdef USE_SOCKETCALL
# define paccept(fd, addr, addrlen, mask, flags) \
({ long args[6] = { \
(long) fd, (long) addr, (long) addrlen, (long) mask, 8, (long) flags }; \
syscall (__NR_socketcall, SYS_PACCEPT, args); })
#else
# define paccept(fd, addr, addrlen, mask, flags) \
syscall (__NR_paccept, fd, addr, addrlen, mask, 8, flags)
#endif
#define PORT 57392
#define SOCK_NONBLOCK O_NONBLOCK
static pthread_barrier_t b;
static void *
tf (void *arg)
{
pthread_barrier_wait (&b);
int s = socket (AF_INET, SOCK_STREAM, 0);
struct sockaddr_in sin;
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = htonl (INADDR_LOOPBACK);
sin.sin_port = htons (PORT);
connect (s, (const struct sockaddr *) &sin, sizeof (sin));
close (s);
pthread_barrier_wait (&b);
pthread_barrier_wait (&b);
s = socket (AF_INET, SOCK_STREAM, 0);
sin.sin_port = htons (PORT);
connect (s, (const struct sockaddr *) &sin, sizeof (sin));
close (s);
pthread_barrier_wait (&b);
return NULL;
}
int
main (void)
{
int fd;
fd = socket (PF_INET, SOCK_STREAM, 0);
if (fd == -1)
{
puts ("socket(0) failed");
return 1;
}
int fl = fcntl (fd, F_GETFL);
if (fl == -1)
{
puts ("fcntl failed");
return 1;
}
if (fl & O_NONBLOCK)
{
puts ("socket(0) set non-blocking mode");
return 1;
}
close (fd);
fd = socket (PF_INET, SOCK_STREAM|SOCK_NONBLOCK, 0);
if (fd == -1)
{
puts ("socket(SOCK_NONBLOCK) failed");
return 1;
}
fl = fcntl (fd, F_GETFL);
if (fl == -1)
{
puts ("fcntl failed");
return 1;
}
if ((fl & O_NONBLOCK) == 0)
{
puts ("socket(SOCK_NONBLOCK) does not set non-blocking mode");
return 1;
}
close (fd);
int fds[2];
if (socketpair (PF_UNIX, SOCK_STREAM, 0, fds) == -1)
{
puts ("socketpair(0) failed");
return 1;
}
for (int i = 0; i < 2; ++i)
{
fl = fcntl (fds[i], F_GETFL);
if (fl == -1)
{
puts ("fcntl failed");
return 1;
}
if (fl & O_NONBLOCK)
{
printf ("socketpair(0) set non-blocking mode for fds[%d]\n", i);
return 1;
}
close (fds[i]);
}
if (socketpair (PF_UNIX, SOCK_STREAM|SOCK_NONBLOCK, 0, fds) == -1)
{
puts ("socketpair(SOCK_NONBLOCK) failed");
return 1;
}
for (int i = 0; i < 2; ++i)
{
fl = fcntl (fds[i], F_GETFL);
if (fl == -1)
{
puts ("fcntl failed");
return 1;
}
if ((fl & O_NONBLOCK) == 0)
{
printf ("socketpair(SOCK_NONBLOCK) does not set non-blocking mode for fds[%d]\n", i);
return 1;
}
close (fds[i]);
}
pthread_barrier_init (&b, NULL, 2);
struct sockaddr_in sin;
pthread_t th;
if (pthread_create (&th, NULL, tf, NULL) != 0)
{
puts ("pthread_create failed");
return 1;
}
int s = socket (AF_INET, SOCK_STREAM, 0);
int reuse = 1;
setsockopt (s, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof (reuse));
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = htonl (INADDR_LOOPBACK);
sin.sin_port = htons (PORT);
bind (s, (struct sockaddr *) &sin, sizeof (sin));
listen (s, SOMAXCONN);
pthread_barrier_wait (&b);
int s2 = paccept (s, NULL, 0, NULL, 0);
if (s2 < 0)
{
puts ("paccept(0) failed");
return 1;
}
fl = fcntl (s2, F_GETFL);
if (fl & O_NONBLOCK)
{
puts ("paccept(0) set non-blocking mode");
return 1;
}
close (s2);
close (s);
pthread_barrier_wait (&b);
s = socket (AF_INET, SOCK_STREAM, 0);
sin.sin_port = htons (PORT);
setsockopt (s, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof (reuse));
bind (s, (struct sockaddr *) &sin, sizeof (sin));
listen (s, SOMAXCONN);
pthread_barrier_wait (&b);
s2 = paccept (s, NULL, 0, NULL, SOCK_NONBLOCK);
if (s2 < 0)
{
puts ("paccept(SOCK_NONBLOCK) failed");
return 1;
}
fl = fcntl (s2, F_GETFL);
if ((fl & O_NONBLOCK) == 0)
{
puts ("paccept(SOCK_NONBLOCK) does not set non-blocking mode");
return 1;
}
close (s2);
close (s);
pthread_barrier_wait (&b);
puts ("OK");
return 0;
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Signed-off-by: 
Ulrich Drepper <drepper@redhat.com>
Acked-by: 
Davide Libenzi <davidel@xmailserver.org>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: 
Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: 
Linus Torvalds <torvalds@linux-foundation.org>
Showing
Please register or sign in to comment