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os: wrap recvmsg(MSG_CMSG_CLOEXEC)

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Some system C libraries do not have MSG_CMSG_CLOEXEC. This flag would
automatically set O_CLOEXEC flag on any received file descriptors.

Provide a fallback that does it manually. If setting CLOEXEC fails, the
file descriptor is closed immediately, which will lead to failures but
avoid leaks. However, setting CLOEXEC is not really expected to fail
occasionally.

Add tests for the wrapper. The setup is copied from connection-test.c.

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>
This commit is contained in:
Pekka Paalanen 2012-03-21 16:00:23 +02:00
parent 2ccaf918ab
commit 35d5053c62
4 changed files with 229 additions and 1 deletions
Download patch file Download diff file Expand all files Collapse all files

2
src/connection.c
View file

@ -307,7 +307,7 @@ wl_connection_data(struct wl_connection *connection, uint32_t mask)
msg.msg_flags = 0;
do {
len = recvmsg(connection->fd, &msg, MSG_CMSG_CLOEXEC);
len = wl_os_recvmsg_cloexec(connection->fd, &msg, 0);
} while (len < 0 && errno == EINTR);
if (len < 0) {

45
src/wayland-os.c
View file

@ -79,3 +79,48 @@ wl_os_dupfd_cloexec(int fd, long minfd)
newfd = fcntl(fd, F_DUPFD, minfd);
return set_cloexec_or_close(newfd);
}
static ssize_t
recvmsg_cloexec_fallback(int sockfd, struct msghdr *msg, int flags)
{
ssize_t len;
struct cmsghdr *cmsg;
unsigned char *data;
int *fd;
int *end;
len = recvmsg(sockfd, msg, flags);
if (len == -1)
return -1;
if (!msg->msg_control || msg->msg_controllen == 0)
return len;
cmsg = CMSG_FIRSTHDR(msg);
for (; cmsg != NULL; cmsg = CMSG_NXTHDR(msg, cmsg)) {
if (cmsg->cmsg_level != SOL_SOCKET ||
cmsg->cmsg_type != SCM_RIGHTS)
continue;
data = CMSG_DATA(cmsg);
end = (int *)(data + cmsg->cmsg_len - CMSG_LEN(0));
for (fd = (int *)data; fd < end; ++fd)
*fd = set_cloexec_or_close(*fd);
}
return len;
}
ssize_t
wl_os_recvmsg_cloexec(int sockfd, struct msghdr *msg, int flags)
{
ssize_t len;
len = recvmsg(sockfd, msg, flags | MSG_CMSG_CLOEXEC);
if (len >= 0)
return len;
if (errno != EINVAL)
return -1;
return recvmsg_cloexec_fallback(sockfd, msg, flags);
}

8
src/wayland-os.h
View file

@ -29,6 +29,10 @@ wl_os_socket_cloexec(int domain, int type, int protocol);
int
wl_os_dupfd_cloexec(int fd, long minfd);
ssize_t
wl_os_recvmsg_cloexec(int sockfd, struct msghdr *msg, int flags);
/*
* The following are for wayland-os.c and the unit tests.
* Do not use them elsewhere.
@ -44,6 +48,10 @@ wl_os_dupfd_cloexec(int fd, long minfd);
#define F_DUPFD_CLOEXEC 1030
#endif
#ifndef MSG_CMSG_CLOEXEC
#define MSG_CMSG_CLOEXEC 0x40000000
#endif
#endif /* __linux__ */
#endif