[patch] accept4
Jilles Tjoelker
jilles at stack.nl
Fri Apr 19 22:48:56 UTC 2013
The accept4() function, compared to accept(), allows setting the new
file descriptor atomically close-on-exec and explicitly controlling the
non-blocking status on the new socket. (Note that the latter point means
that accept() is not equivalent to any form of accept4().)
The linuxulator's accept4 implementation leaves a race window where the
new file descriptor is not close-on-exec because it calls sys_accept().
This implementation leaves no such race window (by using falloc()
flags). The linuxulator could be fixed and simplified by using the new
code.
The comms/openobex port now compiles again without the
patch-lib_cloexec.h patch.
More information about API extensions to set new file descriptors
atomically close-on-exec is at
https://wiki.freebsd.org/AtomicCloseOnExec
I'm also working on pipe2() (using linuxulator work) and dup3() (patch
from Jukka A. Ukkonen).
commit 2e410d9260d12328b689b0938e09d09649b0460a
Author: Jilles Tjoelker <jilles at stack.nl>
Date: Sat Mar 30 21:44:14 2013 +0100
Add accept4() system call.
diff --git a/lib/libc/sys/Makefile.inc b/lib/libc/sys/Makefile.inc
index fef0f3c..105f469 100644
--- a/lib/libc/sys/Makefile.inc
+++ b/lib/libc/sys/Makefile.inc
@@ -270,6 +270,7 @@ MAN+= sctp_generic_recvmsg.2 \
wait.2 \
write.2
+MLINKS+=accept.2 accept4.2
MLINKS+=access.2 eaccess.2 \
access.2 faccessat.2
MLINKS+=brk.2 sbrk.2
diff --git a/lib/libc/sys/Symbol.map b/lib/libc/sys/Symbol.map
index 6faa0af..149fa41 100644
--- a/lib/libc/sys/Symbol.map
+++ b/lib/libc/sys/Symbol.map
@@ -378,6 +378,7 @@ FBSD_1.2 {
};
FBSD_1.3 {
+ accept4;
bindat;
cap_fcntls_get;
cap_fcntls_limit;
@@ -461,6 +462,8 @@ FBSDprivate_1.0 {
__sys_abort2;
_accept;
__sys_accept;
+ _accept4;
+ __sys_accept4;
_access;
__sys_access;
_acct;
diff --git a/lib/libc/sys/accept.2 b/lib/libc/sys/accept.2
index 978b948..e8bccaf 100644
--- a/lib/libc/sys/accept.2
+++ b/lib/libc/sys/accept.2
@@ -41,6 +41,8 @@
.In sys/socket.h
.Ft int
.Fn accept "int s" "struct sockaddr * restrict addr" "socklen_t * restrict addrlen"
+.Ft int
+.Fn accept4 "int s" "struct sockaddr * restrict addr" "socklen_t * restrict addrlen" "int flags"
.Sh DESCRIPTION
The argument
.Fa s
@@ -66,6 +68,26 @@ and
signals from the original socket
.Fa s .
.Pp
+The
+.Fn accept4
+system call is similar,
+but the
+.Dv O_NONBLOCK
+property of the new socket is instead determined by the
+.Dv SOCK_NONBLOCK
+flag in the
+.Fa flags
+argument,
+the
+.Dv O_ASYNC
+property is cleared,
+the signal destination is cleared
+and the close-on-exec flag on the new file descriptor can be set via the
+.Dv SOCK_CLOEXEC
+flag in the
+.Fa flags
+argument.
+.Pp
If no pending connections are
present on the queue, and the original socket
is not marked as non-blocking,
@@ -141,13 +163,15 @@ properties and the signal destination being inherited,
but should set them explicitly using
.Xr fcntl 2 .
.Sh RETURN VALUES
-The call returns \-1 on error.
-If it succeeds, it returns a non-negative
+These calls return \-1 on error.
+If they succeed, they return a non-negative
integer that is a descriptor for the accepted socket.
.Sh ERRORS
The
.Fn accept
-system call will fail if:
+and
+.Fn accept4
+system calls will fail if:
.Bl -tag -width Er
.It Bq Er EBADF
The descriptor is invalid.
@@ -180,6 +204,16 @@ are present to be accepted.
A connection arrived, but it was closed while waiting
on the listen queue.
.El
+.Pp
+The
+.Fn accept4
+system call will also fail if:
+.Bl -tag -width Er
+.It Bq Er EINVAL
+The
+.Fa flags
+argument is invalid.
+.El
.Sh SEE ALSO
.Xr bind 2 ,
.Xr connect 2 ,
@@ -194,3 +228,8 @@ The
.Fn accept
system call appeared in
.Bx 4.2 .
+.Pp
+The
+.Fn accept4
+system call appeared in
+.Fx 10.0 .
diff --git a/lib/libthr/pthread.map b/lib/libthr/pthread.map
index 355edea..bbbd930e 100644
--- a/lib/libthr/pthread.map
+++ b/lib/libthr/pthread.map
@@ -181,6 +181,7 @@ FBSDprivate_1.0 {
___wait;
___waitpid;
__accept;
+ __accept4;
__aio_suspend;
__close;
__connect;
@@ -408,3 +409,7 @@ FBSD_1.2 {
setcontext;
swapcontext;
};
+
+FBSD_1.3 {
+ accept4;
+};
diff --git a/lib/libthr/thread/thr_syscalls.c b/lib/libthr/thread/thr_syscalls.c
index 2327d74..7a08302 100644
--- a/lib/libthr/thread/thr_syscalls.c
+++ b/lib/libthr/thread/thr_syscalls.c
@@ -101,6 +101,7 @@ extern pid_t __waitpid(pid_t, int *, int);
extern int __sys_aio_suspend(const struct aiocb * const[], int,
const struct timespec *);
extern int __sys_accept(int, struct sockaddr *, socklen_t *);
+extern int __sys_accept4(int, struct sockaddr *, socklen_t *, int);
extern int __sys_connect(int, const struct sockaddr *, socklen_t);
extern int __sys_fsync(int);
extern int __sys_msync(void *, size_t, int);
@@ -129,6 +130,7 @@ int ___usleep(useconds_t useconds);
pid_t ___wait(int *);
pid_t ___waitpid(pid_t, int *, int);
int __accept(int, struct sockaddr *, socklen_t *);
+int __accept4(int, struct sockaddr *, socklen_t *, int);
int __aio_suspend(const struct aiocb * const iocbs[], int,
const struct timespec *);
int __close(int);
@@ -176,6 +178,26 @@ __accept(int s, struct sockaddr *addr, socklen_t *addrlen)
return (ret);
}
+__weak_reference(__accept4, accept4);
+
+/*
+ * Cancellation behavior:
+ * If thread is canceled, no socket is created.
+ */
+int
+__accept4(int s, struct sockaddr *addr, socklen_t *addrlen, int flags)
+{
+ struct pthread *curthread;
+ int ret;
+
+ curthread = _get_curthread();
+ _thr_cancel_enter(curthread);
+ ret = __sys_accept4(s, addr, addrlen, flags);
+ _thr_cancel_leave(curthread, ret == -1);
+
+ return (ret);
+}
+
__weak_reference(__aio_suspend, aio_suspend);
int
diff --git a/sys/compat/freebsd32/syscalls.master b/sys/compat/freebsd32/syscalls.master
index 0a40ab2..2cbdf31 100644
--- a/sys/compat/freebsd32/syscalls.master
+++ b/sys/compat/freebsd32/syscalls.master
@@ -1022,3 +1022,7 @@
int namelen); }
540 AUE_CHFLAGSAT NOPROTO { int chflagsat(int fd, const char *path, \
u_long flags, int atflag); }
+541 AUE_ACCEPT NOPROTO { int accept4(int s, \
+ struct sockaddr * __restrict name, \
+ __socklen_t * __restrict anamelen, \
+ int flags); }
diff --git a/sys/kern/capabilities.conf b/sys/kern/capabilities.conf
index f54c25d..0b64503 100644
--- a/sys/kern/capabilities.conf
+++ b/sys/kern/capabilities.conf
@@ -78,6 +78,7 @@ abort2
## relies on existing bindings on a socket, subject to capability rights.
##
accept
+accept4
##
## Allow AIO operations by file descriptor, subject to capability rights.
diff --git a/sys/kern/syscalls.master b/sys/kern/syscalls.master
index 4b3348f..922db30 100644
--- a/sys/kern/syscalls.master
+++ b/sys/kern/syscalls.master
@@ -972,5 +972,9 @@
int namelen); }
540 AUE_CHFLAGSAT STD { int chflagsat(int fd, const char *path, \
u_long flags, int atflag); }
+541 AUE_ACCEPT STD { int accept4(int s, \
+ struct sockaddr * __restrict name, \
+ __socklen_t * __restrict anamelen, \
+ int flags); }
; Please copy any additions and changes to the following compatability tables:
; sys/compat/freebsd32/syscalls.master
diff --git a/sys/kern/uipc_syscalls.c b/sys/kern/uipc_syscalls.c
index ac2fd42..4bbd595 100644
--- a/sys/kern/uipc_syscalls.c
+++ b/sys/kern/uipc_syscalls.c
@@ -97,10 +97,18 @@ __FBSDID("$FreeBSD$");
#endif /* SCTP */
#endif /* INET || INET6 */
+/*
+ * Flags for accept1() and kern_accept4(), in addition to SOCK_CLOEXEC
+ * and SOCK_NONBLOCK.
+ */
+#define ACCEPT4_INHERIT 0x1
+#define ACCEPT4_COMPAT 0x2
+
static int sendit(struct thread *td, int s, struct msghdr *mp, int flags);
static int recvit(struct thread *td, int s, struct msghdr *mp, void *namelenp);
-static int accept1(struct thread *td, struct accept_args *uap, int compat);
+static int accept1(struct thread *td, int s, struct sockaddr *uname,
+ socklen_t *anamelen, int flags);
static int do_sendfile(struct thread *td, struct sendfile_args *uap, int compat);
static int getsockname1(struct thread *td, struct getsockname_args *uap,
int compat);
@@ -317,49 +325,46 @@ sys_listen(td, uap)
* accept1()
*/
static int
-accept1(td, uap, compat)
+accept1(td, s, uname, anamelen, flags)
struct thread *td;
- struct accept_args /* {
- int s;
- struct sockaddr * __restrict name;
- socklen_t * __restrict anamelen;
- } */ *uap;
- int compat;
+ int s;
+ struct sockaddr *uname;
+ socklen_t *anamelen;
+ int flags;
{
struct sockaddr *name;
socklen_t namelen;
struct file *fp;
int error;
- if (uap->name == NULL)
- return (kern_accept(td, uap->s, NULL, NULL, NULL));
+ if (uname == NULL)
+ return (kern_accept4(td, s, NULL, NULL, flags, NULL));
- error = copyin(uap->anamelen, &namelen, sizeof (namelen));
+ error = copyin(anamelen, &namelen, sizeof (namelen));
if (error)
return (error);
- error = kern_accept(td, uap->s, &name, &namelen, &fp);
+ error = kern_accept4(td, s, &name, &namelen, flags, &fp);
/*
* return a namelen of zero for older code which might
* ignore the return value from accept.
*/
if (error) {
- (void) copyout(&namelen,
- uap->anamelen, sizeof(*uap->anamelen));
+ (void) copyout(&namelen, anamelen, sizeof(*anamelen));
return (error);
}
- if (error == 0 && name != NULL) {
+ if (error == 0 && uname != NULL) {
#ifdef COMPAT_OLDSOCK
- if (compat)
+ if (flags & ACCEPT4_COMPAT)
((struct osockaddr *)name)->sa_family =
name->sa_family;
#endif
- error = copyout(name, uap->name, namelen);
+ error = copyout(name, uname, namelen);
}
if (error == 0)
- error = copyout(&namelen, uap->anamelen,
+ error = copyout(&namelen, anamelen,
sizeof(namelen));
if (error)
fdclose(td->td_proc->p_fd, fp, td->td_retval[0], td);
@@ -372,6 +377,13 @@ int
kern_accept(struct thread *td, int s, struct sockaddr **name,
socklen_t *namelen, struct file **fp)
{
+ return (kern_accept4(td, s, name, namelen, ACCEPT4_INHERIT, fp));
+}
+
+int
+kern_accept4(struct thread *td, int s, struct sockaddr **name,
+ socklen_t *namelen, int flags, struct file **fp)
+{
struct filedesc *fdp;
struct file *headfp, *nfp = NULL;
struct sockaddr *sa = NULL;
@@ -400,7 +412,7 @@ kern_accept(struct thread *td, int s, struct sockaddr **name,
if (error != 0)
goto done;
#endif
- error = falloc(td, &nfp, &fd, 0);
+ error = falloc(td, &nfp, &fd, (flags & SOCK_CLOEXEC) ? O_CLOEXEC : 0);
if (error)
goto done;
ACCEPT_LOCK();
@@ -441,7 +453,10 @@ kern_accept(struct thread *td, int s, struct sockaddr **name,
TAILQ_REMOVE(&head->so_comp, so, so_list);
head->so_qlen--;
- so->so_state |= (head->so_state & SS_NBIO);
+ if (flags & ACCEPT4_INHERIT)
+ so->so_state |= (head->so_state & SS_NBIO);
+ else
+ so->so_state |= (flags & SOCK_NONBLOCK) ? SS_NBIO : 0;
so->so_qstate &= ~SQ_COMP;
so->so_head = NULL;
@@ -454,9 +469,15 @@ kern_accept(struct thread *td, int s, struct sockaddr **name,
/* connection has been removed from the listen queue */
KNOTE_UNLOCKED(&head->so_rcv.sb_sel.si_note, 0);
- pgid = fgetown(&head->so_sigio);
- if (pgid != 0)
- fsetown(pgid, &so->so_sigio);
+ if (flags & ACCEPT4_INHERIT) {
+ pgid = fgetown(&head->so_sigio);
+ if (pgid != 0)
+ fsetown(pgid, &so->so_sigio);
+ } else {
+ fflag &= ~(FNONBLOCK | FASYNC);
+ if (flags & SOCK_NONBLOCK)
+ fflag |= FNONBLOCK;
+ }
finit(nfp, fflag, DTYPE_SOCKET, so, &socketops);
/* Sync socket nonblocking/async state with file flags */
@@ -527,7 +548,18 @@ sys_accept(td, uap)
struct accept_args *uap;
{
- return (accept1(td, uap, 0));
+ return (accept1(td, uap->s, uap->name, uap->anamelen, ACCEPT4_INHERIT));
+}
+
+int
+sys_accept4(td, uap)
+ struct thread *td;
+ struct accept4_args *uap;
+{
+ if (uap->flags & ~(SOCK_CLOEXEC | SOCK_NONBLOCK))
+ return (EINVAL);
+
+ return (accept1(td, uap->s, uap->name, uap->anamelen, uap->flags));
}
#ifdef COMPAT_OLDSOCK
@@ -537,7 +569,8 @@ oaccept(td, uap)
struct accept_args *uap;
{
- return (accept1(td, uap, 1));
+ return (accept1(td, uap->s, uap->name, uap->anamelen,
+ ACCEPT4_INHERIT | ACCEPT4_COMPAT));
}
#endif /* COMPAT_OLDSOCK */
diff --git a/sys/sys/socket.h b/sys/sys/socket.h
index 41c85b6..90411d7 100644
--- a/sys/sys/socket.h
+++ b/sys/sys/socket.h
@@ -634,6 +634,7 @@ int accept(int, struct sockaddr * __restrict, socklen_t * __restrict);
int bind(int, const struct sockaddr *, socklen_t);
int connect(int, const struct sockaddr *, socklen_t);
#if __BSD_VISIBLE
+int accept4(int, struct sockaddr * __restrict, socklen_t * __restrict, int);
int bindat(int, int, const struct sockaddr *, socklen_t);
int connectat(int, int, const struct sockaddr *, socklen_t);
#endif
diff --git a/sys/sys/syscallsubr.h b/sys/sys/syscallsubr.h
index fa0d351..49e8be1 100644
--- a/sys/sys/syscallsubr.h
+++ b/sys/sys/syscallsubr.h
@@ -60,6 +60,8 @@ int kern___getcwd(struct thread *td, u_char *buf, enum uio_seg bufseg,
u_int buflen);
int kern_accept(struct thread *td, int s, struct sockaddr **name,
socklen_t *namelen, struct file **fp);
+int kern_accept4(struct thread *td, int s, struct sockaddr **name,
+ socklen_t *namelen, int flags, struct file **fp);
int kern_access(struct thread *td, char *path, enum uio_seg pathseg,
int flags);
int kern_accessat(struct thread *td, int fd, char *path,
--
Jilles Tjoelker
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