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authorYu Watanabe <watanabe.yu+github@gmail.com>2017-03-21 13:34:52 +0900
committerYu Watanabe <watanabe.yu+github@gmail.com>2017-03-21 13:34:52 +0900
commit71a047d2f7ca37bb8e20e94622e94240f8812649 (patch)
tree2d2e112d74092107d67f8da8dceb3dff67859e1f /src/resolve
parentc6a8f6f66da111a417cef7be81ceb9a8f336e541 (diff)
resolved: detect and warn other running mDNS stack
Previously, `SO_REUSEADDR` is set before `bind`-ing socket, Thus, even if another mDNS stack (e.g. avahi) is running, `bind` always success and we cannot detect the other stack. By this commit, we first try to `bind` without `SO_REUSEADDR`, and if it fails, show warning and retry with `SO_REUSEADDR`.
Diffstat (limited to 'src/resolve')
-rw-r--r--src/resolve/resolved-mdns.c102
1 files changed, 71 insertions, 31 deletions
diff --git a/src/resolve/resolved-mdns.c b/src/resolve/resolved-mdns.c
index c40e8f75f0..415dc1a532 100644
--- a/src/resolve/resolved-mdns.c
+++ b/src/resolve/resolved-mdns.c
@@ -60,7 +60,7 @@ int manager_mdns_start(Manager *m) {
return 0;
eaddrinuse:
- log_warning("There appears to be another mDNS responder running. Turning off mDNS support.");
+ log_warning("Another mDNS responder prohibits binding the socket to the same port. Turning off mDNS support.");
m->mdns_support = RESOLVE_SUPPORT_NO;
manager_mdns_stop(m);
@@ -217,55 +217,75 @@ int manager_mdns_ipv4_fd(Manager *m) {
m->mdns_ipv4_fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
if (m->mdns_ipv4_fd < 0)
- return -errno;
+ return log_error_errno(errno, "mDNS-IPv4: Failed to create socket: %m");
r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_TTL, &ttl, sizeof(ttl));
if (r < 0) {
- r = -errno;
+ r = log_error_errno(errno, "mDNS-IPv4: Failed to set IP_TTL: %m");
goto fail;
}
r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl));
if (r < 0) {
- r = -errno;
+ r = log_error_errno(errno, "mDNS-IPv4: Failed to set IP_MULTICAST_TTL: %m");
goto fail;
}
r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_MULTICAST_LOOP, &one, sizeof(one));
if (r < 0) {
- r = -errno;
- goto fail;
- }
-
- r = setsockopt(m->mdns_ipv4_fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
- if (r < 0) {
- r = -errno;
+ r = log_error_errno(errno, "mDNS-IPv4: Failed to set IP_MULTICAST_LOOP: %m");
goto fail;
}
r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_PKTINFO, &one, sizeof(one));
if (r < 0) {
- r = -errno;
+ r = log_error_errno(errno, "mDNS-IPv4: Failed to set IP_PKTINFO: %m");
goto fail;
}
r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_RECVTTL, &one, sizeof(one));
if (r < 0) {
- r = -errno;
+ r = log_error_errno(errno, "mDNS-IPv4: Failed to set IP_RECVTTL: %m");
goto fail;
}
/* Disable Don't-Fragment bit in the IP header */
r = setsockopt(m->mdns_ipv4_fd, IPPROTO_IP, IP_MTU_DISCOVER, &pmtu, sizeof(pmtu));
if (r < 0) {
- r = -errno;
+ r = log_error_errno(errno, "mDNS-IPv4: Failed to set IP_MTU_DISCOVER: %m");
goto fail;
}
+ /* See the section 15.1 of RFC6762 */
+ /* first try to bind without SO_REUSEADDR to detect another mDNS responder */
r = bind(m->mdns_ipv4_fd, &sa.sa, sizeof(sa.in));
if (r < 0) {
- r = -errno;
- goto fail;
+ if (errno != EADDRINUSE) {
+ r = log_error_errno(errno, "mDNS-IPv4: Failed to bind socket: %m");
+ goto fail;
+ }
+
+ log_warning("mDNS-IPv4: There appears to be another mDNS responder running, or previously systemd-resolved crashed with some outstanding transfers.");
+
+ /* try again with SO_REUSEADDR */
+ r = setsockopt(m->mdns_ipv4_fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
+ if (r < 0) {
+ r = log_error_errno(errno, "mDNS-IPv4: Failed to set SO_REUSEADDR: %m");
+ goto fail;
+ }
+
+ r = bind(m->mdns_ipv4_fd, &sa.sa, sizeof(sa.in));
+ if (r < 0) {
+ r = log_error_errno(errno, "mDNS-IPv4: Failed to bind socket: %m");
+ goto fail;
+ }
+ } else {
+ /* enable SO_REUSEADDR for the case that the user really wants multiple mDNS responders */
+ r = setsockopt(m->mdns_ipv4_fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
+ if (r < 0) {
+ r = log_error_errno(errno, "mDNS-IPv4: Failed to set SO_REUSEADDR: %m");
+ goto fail;
+ }
}
r = sd_event_add_io(m->event, &m->mdns_ipv4_event_source, m->mdns_ipv4_fd, EPOLLIN, on_mdns_packet, m);
@@ -294,55 +314,75 @@ int manager_mdns_ipv6_fd(Manager *m) {
m->mdns_ipv6_fd = socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
if (m->mdns_ipv6_fd < 0)
- return -errno;
+ return log_error_errno(errno, "mDNS-IPv6: Failed to create socket: %m");
r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &ttl, sizeof(ttl));
if (r < 0) {
- r = -errno;
+ r = log_error_errno(errno, "mDNS-IPv6: Failed to set IPV6_UNICAST_HOPS: %m");
goto fail;
}
/* RFC 4795, section 2.5 recommends setting the TTL of UDP packets to 255. */
r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &ttl, sizeof(ttl));
if (r < 0) {
- r = -errno;
+ r = log_error_errno(errno, "mDNS-IPv6: Failed to set IPV6_MULTICAST_HOPS: %m");
goto fail;
}
r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &one, sizeof(one));
if (r < 0) {
- r = -errno;
+ r = log_error_errno(errno, "mDNS-IPv6: Failed to set IPV6_MULTICAST_LOOP: %m");
goto fail;
}
r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_V6ONLY, &one, sizeof(one));
if (r < 0) {
- r = -errno;
- goto fail;
- }
-
- r = setsockopt(m->mdns_ipv6_fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
- if (r < 0) {
- r = -errno;
+ r = log_error_errno(errno, "mDNS-IPv6: Failed to set IPV6_V6ONLY: %m");
goto fail;
}
r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_RECVPKTINFO, &one, sizeof(one));
if (r < 0) {
- r = -errno;
+ r = log_error_errno(errno, "mDNS-IPv6: Failed to set IPV6_RECVPKTINFO: %m");
goto fail;
}
r = setsockopt(m->mdns_ipv6_fd, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &one, sizeof(one));
if (r < 0) {
- r = -errno;
+ r = log_error_errno(errno, "mDNS-IPv6: Failed to set IPV6_RECVHOPLIMIT: %m");
goto fail;
}
+ /* See the section 15.1 of RFC6762 */
+ /* first try to bind without SO_REUSEADDR to detect another mDNS responder */
r = bind(m->mdns_ipv6_fd, &sa.sa, sizeof(sa.in6));
if (r < 0) {
- r = -errno;
- goto fail;
+ if (errno != EADDRINUSE) {
+ r = log_error_errno(errno, "mDNS-IPv6: Failed to bind socket: %m");
+ goto fail;
+ }
+
+ log_warning("mDNS-IPv6: There appears to be another mDNS responder running, or previously systemd-resolved crashed with some outstanding transfers.");
+
+ /* try again with SO_REUSEADDR */
+ r = setsockopt(m->mdns_ipv6_fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
+ if (r < 0) {
+ r = log_error_errno(errno, "mDNS-IPv6: Failed to set SO_REUSEADDR: %m");
+ goto fail;
+ }
+
+ r = bind(m->mdns_ipv6_fd, &sa.sa, sizeof(sa.in6));
+ if (r < 0) {
+ r = log_error_errno(errno, "mDNS-IPv6: Failed to bind socket: %m");
+ goto fail;
+ }
+ } else {
+ /* enable SO_REUSEADDR for the case that the user really wants multiple mDNS responders */
+ r = setsockopt(m->mdns_ipv6_fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
+ if (r < 0) {
+ r = log_error_errno(errno, "mDNS-IPv6: Failed to set SO_REUSEADDR: %m");
+ goto fail;
+ }
}
r = sd_event_add_io(m->event, &m->mdns_ipv6_event_source, m->mdns_ipv6_fd, EPOLLIN, on_mdns_packet, m);