lib/tsocket: check for errors indicated by poll() before getsockopt(fd, SOL_SOCKET, SO_ERROR)

This also returns an error if we got TCP_FIN from the peer,
which is only reported by an explicit POLLRDHUP check.

Also on FreeBSD getsockopt(fd, SOL_SOCKET, SO_ERROR) fetches
and resets the error, so a 2nd call no longer returns an error.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15202

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>

1 files changed, 79 insertions, 1 deletions

diff --git a/lib/tsocket/tsocket_bsd.c b/lib/tsocket/tsocket_bsd.c
index a4c2d0cf336..8ab2ffb0b83 100644
--- a/lib/tsocket/tsocket_bsd.c
+++ b/lib/tsocket/tsocket_bsd.c
@@ -24,8 +24,10 @@
 #include "replace.h"
 #include "system/filesys.h"
 #include "system/network.h"
+#include "system/select.h"
 #include "tsocket.h"
 #include "tsocket_internal.h"
+#include "lib/util/select.h"
 #include "lib/util/iov_buf.h"
 #include "lib/util/blocking.h"
 #include "lib/util/util_net.h"
@@ -171,7 +173,42 @@ static ssize_t tsocket_bsd_netlink_pending(int fd)
 }
 #endif
 
-static ssize_t tsocket_bsd_error(int fd)
+static int tsocket_bsd_poll_error(int fd)
+{
+	struct pollfd pfd = {
+		.fd = fd,
+#ifdef POLLRDHUP
+		.events = POLLRDHUP, /* POLLERR and POLLHUP are not needed */
+#endif
+	};
+	int ret;
+
+	errno = 0;
+	ret = sys_poll_intr(&pfd, 1, 0);
+	if (ret == 0) {
+		return 0;
+	}
+	if (ret != 1) {
+		return POLLNVAL;
+	}
+
+	if (pfd.revents & POLLERR) {
+		return POLLERR;
+	}
+	if (pfd.revents & POLLHUP) {
+		return POLLHUP;
+	}
+#ifdef POLLRDHUP
+	if (pfd.revents & POLLRDHUP) {
+		return POLLRDHUP;
+	}
+#endif
+
+	/* should never be reached! */
+	return POLLNVAL;
+}
+
+static int tsocket_bsd_sock_error(int fd)
 {
 	int ret, error = 0;
 	socklen_t len = sizeof(error);
@@ -192,6 +229,47 @@ static ssize_t tsocket_bsd_error(int fd)
 	return 0;
 }
 
+static int tsocket_bsd_error(int fd)
+{
+	int ret;
+	int poll_error = 0;
+
+	poll_error = tsocket_bsd_poll_error(fd);
+	if (poll_error == 0) {
+		return 0;
+	}
+
+#ifdef POLLRDHUP
+	if (poll_error == POLLRDHUP) {
+		errno = ECONNRESET;
+		return -1;
+	}
+#endif
+
+	if (poll_error == POLLHUP) {
+		errno = EPIPE;
+		return -1;
+	}
+
+	/*
+	 * POLLERR and POLLNVAL fallback to
+	 * getsockopt(fd, SOL_SOCKET, SO_ERROR)
+	 * and force EPIPE as fallback.
+	 */
+
+	errno = 0;
+	ret = tsocket_bsd_sock_error(fd);
+	if (ret == 0) {
+		errno = EPIPE;
+	}
+
+	if (errno == 0) {
+		errno = EPIPE;
+	}
+
+	return -1;
+}
+
 static ssize_t tsocket_bsd_pending(int fd)
 {
 	int ret;