From b9da815deb890443e80e11c73b5084dcfb75ad4f Mon Sep 17 00:00:00 2001 From: Evgeny Vereshchagin Date: Mon, 23 May 2016 11:19:14 +0300 Subject: [PATCH] resolved: don't stop handle messages after receiving a zero length UDP packet (#3323) Fixes: -bash-4.3# ss --udp -l -p State Recv-Q Send-Q Local Address:Port Peer Address:Port UNCONN 0 0 *:5355 *:* users:(("systemd-resolve",pid=601,fd=12)) UNCONN 0 0 :::5355 :::* users:(("systemd-resolve",pid=601,fd=14)) -bash-4.3# nping --udp -p 5355 --data-length 0 -c 1 localhost -bash-4.3# journalctl -u systemd-resolved -b --no-hostname ... May 21 14:59:22 systemd-resolved[601]: Event source llmnr-ipv4-udp (type io) returned error, disabling: Input/output error ... -bash-4.3# nping --udp -p 5355 --data-length 1000 -c 1 localhost -bash-4.3# ss --udp -l State Recv-Q Send-Q Local Address:Port Peer Address:Port UNCONN 2304 0 *:5355 *:* UNCONN 0 0 :::5355 :::* (cherry picked from commit f134289ac59560946e6559d9487e60c7690396ba) --- src/resolve/resolved-manager.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/src/resolve/resolved-manager.c b/src/resolve/resolved-manager.c index 7f9073448a..aeb2b78523 100644 --- a/src/resolve/resolved-manager.c +++ b/src/resolve/resolved-manager.c @@ -643,6 +643,8 @@ int manager_recv(Manager *m, int fd, DnsProtocol protocol, DnsPacket **ret) { mh.msg_controllen = sizeof(control); l = recvmsg(fd, &mh, 0); + if (l == 0) + return 0; if (l < 0) { if (errno == EAGAIN || errno == EINTR) return 0; @@ -650,9 +652,6 @@ int manager_recv(Manager *m, int fd, DnsProtocol protocol, DnsPacket **ret) { return -errno; } - if (l <= 0) - return -EIO; - assert(!(mh.msg_flags & MSG_CTRUNC)); assert(!(mh.msg_flags & MSG_TRUNC));