[PATCH] socket, socketpair w/flags, accept4

From: Ulrich Drepper
Date: Thu Apr 24 2008 - 14:21:17 EST

If Alan's comments reflect the general opinion this patch should have
all the changes. No new sock_map_fd_flags function and there is a
helper function to convert socket flags into file flags.

The new accept syscall is also in. It uses the same SOCK_CLOEXEC
flags. I think everything else is confusing. This is an aspect
where new socket/socketpair syscalls would be better.

The code changes are really minimal. And don't get too hung up on the
internal name of the syscall. I think accept4 is more desriptive than
paccept since a) suffixes more easily indicate derived functionality
and b) the 4 actually indicates to the initiated what has changed.
If there are good reasons otherwise the userlevel interface can still
be something completely different.


#include <fcntl.h>
#include <pthread.h>
#include <stdio.h>
#include <unistd.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/syscall.h>

#define SOCK_CLOEXEC 0x40000000

#ifdef __x86_64__
#define __NR_accept4 288
#elif __i386__
#define SYS_ACCEPT4 18
#define USE_SOCKETCALL 1
#else
#error "define syscall numbers for this architecture"
#endif

#define PORT 57392

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_family = AF_INET;
sin.sin_addr.s_addr = htonl (INADDR_LOOPBACK);
sin.sin_port = htons (PORT + 1);
connect (s, (const struct sockaddr *) &sin, sizeof (sin));
close (s);
return NULL;
}

int
main (void)
{
int status = 0;
int s;
int sp[2];

s = socket (PF_UNIX, SOCK_STREAM, 0);

if (s < 0)
{
puts ("socket failed");
status = 1;
}
else
{
int fl = fcntl (s, F_GETFD);
if ((fl & FD_CLOEXEC) != 0)
{
puts ("socket did set CLOEXEC");
status = 1;
}

close (s);
}

s = socket (PF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0);

if (s < 0)
{
puts ("socket(SOCK_CLOEXEC) failed");
status = 1;
}
else
{
int fl = fcntl (s, F_GETFD);
if ((fl & FD_CLOEXEC) == 0)
{
puts ("socket(SOCK_CLOEXEC) did not set CLOEXEC");
status = 1;
}

close (s);
}

if (socketpair (PF_UNIX, SOCK_STREAM, 0, sp) < 0)
{
puts ("socketpair failed");
status = 1;
}
else
{
int fl1 = fcntl (sp[0], F_GETFD);
int fl2 = fcntl (sp[1], F_GETFD);
if ((fl1 & FD_CLOEXEC) != 0 || (fl2 & FD_CLOEXEC) != 0)
{
puts ("socketpair did set CLOEXEC");
status = 1;
}

close (sp[0]);
close (sp[1]);
}

if (socketpair (PF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0, sp) < 0)
{
puts ("socketpair(SOCK_CLOEXEC) failed");
status = 1;
}
else
{
int fl1 = fcntl (sp[0], F_GETFD);
int fl2 = fcntl (sp[1], F_GETFD);
if ((fl1 & FD_CLOEXEC) == 0 || (fl2 & FD_CLOEXEC) == 0)
{
puts ("socketpair(SOCK_CLOEXEC) did not set CLOEXEC");
status = 1;
}

close (sp[0]);
close (sp[1]);
}

pthread_barrier_init (&b, NULL, 2);

pthread_t th;
if (pthread_create (&th, NULL, tf, NULL) != 0)
{
puts ("pthread_create failed");
status = 1;
}
else
{
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);
bind (s, (struct sockaddr *) &sin, sizeof (sin));
listen (s, SOMAXCONN);

pthread_barrier_wait (&b);

int s2 = accept (s, NULL, 0);
if (s2 < 0)
{
puts ("accept failed");
status = 1;
}
else
{
int fl = fcntl (s2, F_GETFD);
if ((fl & FD_CLOEXEC) != 0)
{
puts ("accept did set CLOEXEC");
status = 1;
}

close (s2);
}

close (s);

pthread_barrier_wait (&b);

sin.sin_family = AF_INET;
sin.sin_addr.s_addr = htonl (INADDR_LOOPBACK);
sin.sin_port = htons (PORT + 1);
s = socket (AF_INET, SOCK_STREAM, 0);
bind (s, (struct sockaddr *) &sin, sizeof (sin));
listen (s, SOMAXCONN);

pthread_barrier_wait (&b);

#if USE_SOCKETCALL
s2 = syscall (__NR_socketcall, SYS_ACCEPT4, s, NULL, 0, SOCK_CLOEXEC);
#else
s2 = syscall (__NR_accept4, s, NULL, 0, SOCK_CLOEXEC);
#endif
if (s2 < 0)
{
puts ("accept4 failed");
status = 1;
}
else
{
int fl = fcntl (s2, F_GETFD);
if ((fl & FD_CLOEXEC) == 0)
{
puts ("accept4 did not set CLOEXEC");
status = 1;
}

close (s2);
}

close (s);
}

return status;
}



include/asm-x86/unistd_64.h | 2 +
include/linux/net.h | 6 +++-
include/linux/syscalls.h | 1
net/compat.c | 12 +++++---
net/socket.c | 62 +++++++++++++++++++++++++++++++++-----------
5 files changed, 63 insertions(+), 20 deletions(-)


Signed-off-by: Ulrich Drepper <drepper@xxxxxxxxxx>

diff --git a/include/asm-x86/unistd_64.h b/include/asm-x86/unistd_64.h
index fe26e36..c7e4abf 100644
--- a/include/asm-x86/unistd_64.h
+++ b/include/asm-x86/unistd_64.h
@@ -639,6 +639,8 @@ __SYSCALL(__NR_fallocate, sys_fallocate)
__SYSCALL(__NR_timerfd_settime, sys_timerfd_settime)
#define __NR_timerfd_gettime 287
__SYSCALL(__NR_timerfd_gettime, sys_timerfd_gettime)
+#define __NR_accept4 288
+__SYSCALL(__NR_accept4, sys_accept4)


#ifndef __NO_STUBS
diff --git a/include/linux/net.h b/include/linux/net.h
index 71f7dd5..133ef65 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -46,6 +46,7 @@ struct net;
#define SYS_GETSOCKOPT 15 /* sys_getsockopt(2) */
#define SYS_SENDMSG 16 /* sys_sendmsg(2) */
#define SYS_RECVMSG 17 /* sys_recvmsg(2) */
+#define SYS_ACCEPT4 18 /* sys_accept4(2) */

typedef enum {
SS_FREE = 0, /* not allocated */
@@ -91,6 +92,9 @@ enum sock_type {
SOCK_SEQPACKET = 5,
SOCK_DCCP = 6,
SOCK_PACKET = 10,
+
+ /* Flag values, ORed to the types above. */
+ SOCK_CLOEXEC = 0x40000000
};

#define SOCK_MAX (SOCK_PACKET + 1)
@@ -208,7 +212,7 @@ extern int sock_sendmsg(struct socket *sock, struct msghdr *msg,
size_t len);
extern int sock_recvmsg(struct socket *sock, struct msghdr *msg,
size_t size, int flags);
-extern int sock_map_fd(struct socket *sock);
+extern int sock_map_fd(struct socket *sock, int flags);
extern struct socket *sockfd_lookup(int fd, int *err);
#define sockfd_put(sock) fput(sock->file)
extern int net_ratelimit(void);
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 8df6d13..42f5ac0 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -407,6 +407,7 @@ asmlinkage long sys_getsockopt(int fd, int level, int optname,
asmlinkage long sys_bind(int, struct sockaddr __user *, int);
asmlinkage long sys_connect(int, struct sockaddr __user *, int);
asmlinkage long sys_accept(int, struct sockaddr __user *, int __user *);
+asmlinkage long sys_accept4(int, struct sockaddr __user *, int __user *, int);
asmlinkage long sys_getsockname(int, struct sockaddr __user *, int __user *);
asmlinkage long sys_getpeername(int, struct sockaddr __user *, int __user *);
asmlinkage long sys_send(int, void __user *, size_t, unsigned);
diff --git a/net/compat.c b/net/compat.c
index 80013fb..b28d568 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -523,9 +523,10 @@ asmlinkage long compat_sys_getsockopt(int fd, int level, int optname,
}
/* Argument list sizes for compat_sys_socketcall */
#define AL(x) ((x) * sizeof(u32))
-static unsigned char nas[18]={AL(0),AL(3),AL(3),AL(3),AL(2),AL(3),
+static unsigned char nas[19]={AL(0),AL(3),AL(3),AL(3),AL(2),AL(3),
AL(3),AL(3),AL(4),AL(4),AL(4),AL(6),
- AL(6),AL(2),AL(5),AL(5),AL(3),AL(3)};
+ AL(6),AL(2),AL(5),AL(5),AL(3),AL(3),
+ AL(4)};
#undef AL

asmlinkage long compat_sys_sendmsg(int fd, struct compat_msghdr __user *msg, unsigned flags)
@@ -544,7 +545,7 @@ asmlinkage long compat_sys_socketcall(int call, u32 __user *args)
u32 a[6];
u32 a0, a1;

- if (call < SYS_SOCKET || call > SYS_RECVMSG)
+ if (call < SYS_SOCKET || call > SYS_ACCEPT4)
return -EINVAL;
if (copy_from_user(a, args, nas[call]))
return -EFAULT;
@@ -565,7 +566,7 @@ asmlinkage long compat_sys_socketcall(int call, u32 __user *args)
ret = sys_listen(a0, a1);
break;
case SYS_ACCEPT:
- ret = sys_accept(a0, compat_ptr(a1), compat_ptr(a[2]));
+ ret = sys_accept4(a0, compat_ptr(a1), compat_ptr(a[2]), 0);
break;
case SYS_GETSOCKNAME:
ret = sys_getsockname(a0, compat_ptr(a1), compat_ptr(a[2]));
@@ -605,6 +606,9 @@ asmlinkage long compat_sys_socketcall(int call, u32 __user *args)
case SYS_RECVMSG:
ret = compat_sys_recvmsg(a0, compat_ptr(a1), a[2]);
break;
+ case SYS_ACCEPT4:
+ ret = sys_accept4(a0, compat_ptr(a1), compat_ptr(a[2]), a[3]);
+ break;
default:
ret = -EINVAL;
break;
diff --git a/net/socket.c b/net/socket.c
index 9b5c917..0859cee 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -348,11 +348,11 @@ static struct dentry_operations sockfs_dentry_operations = {
* but we take care of internal coherence yet.
*/

-static int sock_alloc_fd(struct file **filep)
+static int sock_alloc_fd(struct file **filep, int flags)
{
int fd;

- fd = get_unused_fd();
+ fd = get_unused_fd_flags(flags);
if (likely(fd >= 0)) {
struct file *file = get_empty_filp();

@@ -395,10 +395,10 @@ static int sock_attach_fd(struct socket *sock, struct file *file)
return 0;
}

-int sock_map_fd(struct socket *sock)
+int sock_map_fd(struct socket *sock, int flags)
{
struct file *newfile;
- int fd = sock_alloc_fd(&newfile);
+ int fd = sock_alloc_fd(&newfile, flags);

if (likely(fd >= 0)) {
int err = sock_attach_fd(sock, newfile);
@@ -1213,16 +1213,30 @@ int sock_create_kern(int family, int type, int protocol, struct socket **res)
return __sock_create(&init_net, family, type, protocol, res, 1);
}

+static int sock_to_file_flags(int *sflags)
+{
+ int fflags = 0;
+
+ /* Extract the close-on-exec flag. */
+ if ((*sflags & SOCK_CLOEXEC) != 0) {
+ fflags |= O_CLOEXEC;
+ *sflags &= ~SOCK_CLOEXEC;
+ }
+
+ return fflags;
+}
+
asmlinkage long sys_socket(int family, int type, int protocol)
{
int retval;
struct socket *sock;
+ int fflags = sock_to_file_flags(&type);

retval = sock_create(family, type, protocol, &sock);
if (retval < 0)
goto out;

- retval = sock_map_fd(sock);
+ retval = sock_map_fd(sock, fflags);
if (retval < 0)
goto out_release;

@@ -1245,6 +1259,7 @@ asmlinkage long sys_socketpair(int family, int type, int protocol,
struct socket *sock1, *sock2;
int fd1, fd2, err;
struct file *newfile1, *newfile2;
+ int fflags = sock_to_file_flags(&type);

/*
* Obtain the first socket and check if the underlying protocol
@@ -1263,13 +1278,13 @@ asmlinkage long sys_socketpair(int family, int type, int protocol,
if (err < 0)
goto out_release_both;

- fd1 = sock_alloc_fd(&newfile1);
+ fd1 = sock_alloc_fd(&newfile1, fflags);
if (unlikely(fd1 < 0)) {
err = fd1;
goto out_release_both;
}

- fd2 = sock_alloc_fd(&newfile2);
+ fd2 = sock_alloc_fd(&newfile2, fflags);
if (unlikely(fd2 < 0)) {
err = fd2;
put_filp(newfile1);
@@ -1400,13 +1415,18 @@ asmlinkage long sys_listen(int fd, int backlog)
* clean when we restucture accept also.
*/

-asmlinkage long sys_accept(int fd, struct sockaddr __user *upeer_sockaddr,
- int __user *upeer_addrlen)
+asmlinkage long sys_accept4(int fd, struct sockaddr __user *upeer_sockaddr,
+ int __user *upeer_addrlen, int flags)
{
struct socket *sock, *newsock;
struct file *newfile;
int err, len, newfd, fput_needed;
char address[MAX_SOCK_ADDR];
+ int fflags = sock_to_file_flags(&flags);
+
+ /* So far no additional flags are recognized. */
+ if (unlikely(flags != 0))
+ return -EINVAL;

sock = sockfd_lookup_light(fd, &err, &fput_needed);
if (!sock)
@@ -1425,7 +1445,7 @@ asmlinkage long sys_accept(int fd, struct sockaddr __user *upeer_sockaddr,
*/
__module_get(newsock->ops->owner);

- newfd = sock_alloc_fd(&newfile);
+ newfd = sock_alloc_fd(&newfile, fflags);
if (unlikely(newfd < 0)) {
err = newfd;
sock_release(newsock);
@@ -1478,6 +1498,12 @@ out_fd:
goto out_put;
}

+asmlinkage long sys_accept(int fd, struct sockaddr __user *upeer_sockaddr,
+ int __user *upeer_addrlen)
+{
+ return sys_accept4(fd, upeer_sockaddr, upeer_addrlen, 0);
+}
+
/*
* Attempt to connect to a socket with the server address. The address
* is in user space so we verify it is OK and move it to kernel space.
@@ -1988,10 +2014,11 @@ out:

/* Argument list sizes for sys_socketcall */
#define AL(x) ((x) * sizeof(unsigned long))
-static const unsigned char nargs[18]={
+static const unsigned char nargs[19]={
AL(0),AL(3),AL(3),AL(3),AL(2),AL(3),
AL(3),AL(3),AL(4),AL(4),AL(4),AL(6),
- AL(6),AL(2),AL(5),AL(5),AL(3),AL(3)
+ AL(6),AL(2),AL(5),AL(5),AL(3),AL(3),
+ AL(4)
};

#undef AL
@@ -2010,7 +2037,7 @@ asmlinkage long sys_socketcall(int call, unsigned long __user *args)
unsigned long a0, a1;
int err;

- if (call < 1 || call > SYS_RECVMSG)
+ if (call < 1 || call > SYS_ACCEPT4)
return -EINVAL;

/* copy_from_user should be SMP safe. */
@@ -2039,8 +2066,8 @@ asmlinkage long sys_socketcall(int call, unsigned long __user *args)
break;
case SYS_ACCEPT:
err =
- sys_accept(a0, (struct sockaddr __user *)a1,
- (int __user *)a[2]);
+ sys_accept4(a0, (struct sockaddr __user *)a1,
+ (int __user *)a[2], 0);
break;
case SYS_GETSOCKNAME:
err =
@@ -2087,6 +2114,11 @@ asmlinkage long sys_socketcall(int call, unsigned long __user *args)
case SYS_RECVMSG:
err = sys_recvmsg(a0, (struct msghdr __user *)a1, a[2]);
break;
+ case SYS_ACCEPT4:
+ err =
+ sys_accept4(a0, (struct sockaddr __user *)a1,
+ (int __user *)a[2], a[3]);
+ break;
default:
err = -EINVAL;
break;
--
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