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lib/tsocket: workaround sockets not supporting FIONREAD

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Netlink sockets don't support querying pending bytes with ioctl(fd,
FIONREAD, ...) and would return EOPNOTSUPP, so use recvmsg() with
MSG_PEEK|MSG_TRUNC as a fallback.

The MSG_TRUNC flag to recvmsg() is Linux only, but netlink is as well,
so we're safe for now.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=11714

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>
Reviewed-by: Martin Schwenke <martin@meltin.net>

Autobuild-User(master): Ralph Böhme <slow@samba.org>
Autobuild-Date(master): Wed Feb 10 10:30:24 CET 2016 on sn-devel-144

(cherry picked from commit 574313a1e11d521ba3f7232ff0b4186b49658199)
This commit is contained in:
Ralph Boehme 2016-02-04 15:35:06 +01:00 committed by Karolin Seeger
parent 6774af16ea
commit 4f637ba7df
1 changed files with 61 additions and 1 deletions
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62
lib/tsocket/tsocket_bsd.c
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@ -132,6 +132,43 @@ static int tsocket_bsd_common_prepare_fd(int fd, bool high_fd)
return -1;
}
#ifdef HAVE_LINUX_RTNETLINK_H
/**
* Get the amount of pending bytes from a netlink socket
*
* For some reason netlink sockets don't support querying the amount of pending
* data via ioctl with FIONREAD, which is what we use in tsocket_bsd_pending()
* below.
*
* We know we are on Linux as we're using netlink, which means we have a working
* MSG_TRUNC flag to recvmsg() as well, so we use that together with MSG_PEEK.
**/
static ssize_t tsocket_bsd_netlink_pending(int fd)
{
struct iovec iov;
struct msghdr msg;
char buf[1];
iov = (struct iovec) {
.iov_base = buf,
.iov_len = sizeof(buf)
};
msg = (struct msghdr) {
.msg_iov = &iov,
.msg_iovlen = 1
};
return recvmsg(fd, &msg, MSG_PEEK | MSG_TRUNC);
}
#else
static ssize_t tsocket_bsd_netlink_pending(int fd)
{
errno = ENOSYS;
return -1;
}
#endif
static ssize_t tsocket_bsd_pending(int fd)
{
int ret, error;
@ -640,6 +677,7 @@ struct tdgram_bsd {
void *event_ptr;
struct tevent_fd *fde;
bool optimize_recvfrom;
bool netlink;
void *readable_private;
void (*readable_handler)(void *private_data);
@ -892,7 +930,12 @@ static void tdgram_bsd_recvfrom_handler(void *private_data)
int err;
bool retry;
ret = tsocket_bsd_pending(bsds->fd);
if (bsds->netlink) {
ret = tsocket_bsd_netlink_pending(bsds->fd);
} else {
ret = tsocket_bsd_pending(bsds->fd);
}
if (state->first_try && ret == 0) {
state->first_try = false;
/* retry later */
@ -1395,6 +1438,11 @@ int _tdgram_bsd_existing_socket(TALLOC_CTX *mem_ctx,
{
struct tdgram_context *dgram;
struct tdgram_bsd *bsds;
#ifdef HAVE_LINUX_RTNETLINK_H
int result;
struct sockaddr sa;
socklen_t sa_len = sizeof(struct sockaddr);
#endif
dgram = tdgram_context_create(mem_ctx,
&tdgram_bsd_ops,
@ -1409,6 +1457,18 @@ int _tdgram_bsd_existing_socket(TALLOC_CTX *mem_ctx,
talloc_set_destructor(bsds, tdgram_bsd_destructor);
*_dgram = dgram;
#ifdef HAVE_LINUX_RTNETLINK_H
/*
* Try to determine the protocol family and remember if it's
* AF_NETLINK. We don't care if this fails.
*/
result = getsockname(fd, &sa, &sa_len);
if (result == 0 && sa.sa_family == AF_NETLINK) {
bsds->netlink = true;
}
#endif
return 0;
}