dnsdist: Stop setting SO_REUSEADDR on outgoing UDP client sockets

`SO_REUSEADDR` is useful on TCP server sockets to allow binding quickly
after restarting the process without waiting `TIME_WAIT` seconds, or
to allow some port reuse on BSD. It also allows reusing a port more
quickly for TCP client sockets.
For UDP sockets, however, Linux allows two sockets to be bound to the
same address and port, and will distribute all packets to the most
recent socket, which is very unexpected, to say the least.

(cherry picked from commit b33f09f1989e938c503142a38c556df94254443a)

diff --git a/pdns/dnsdistdist/dnsdist-backend.cc b/pdns/dnsdistdist/dnsdist-backend.cc
index 9113183c83f31d9ea28984f77622cb7eaa152e4c..cfa6e5c7b653e5177b76b603ef147f63dc47d187 100644 (file)
--- a/pdns/dnsdistdist/dnsdist-backend.cc
+++ b/pdns/dnsdistdist/dnsdist-backend.cc
@@ -72,7 +72,6 @@ bool DownstreamState::reconnect()
 #endif
 
     if (!IsAnyAddress(d_config.sourceAddr)) {
-      SSetsockopt(fd, SOL_SOCKET, SO_REUSEADDR, 1);
 #ifdef IP_BIND_ADDRESS_NO_PORT
       if (d_config.ipBindAddrNoPort) {
         SSetsockopt(fd, SOL_IP, IP_BIND_ADDRESS_NO_PORT, 1);

diff --git a/pdns/dnsdistdist/dnsdist-healthchecks.cc b/pdns/dnsdistdist/dnsdist-healthchecks.cc
index 4a5205227626e605de8776a10bc7cdc7b78449c0..fc831e6481e94b051d45d652162a1fe12e46fd0c 100644 (file)
--- a/pdns/dnsdistdist/dnsdist-healthchecks.cc
+++ b/pdns/dnsdistdist/dnsdist-healthchecks.cc
@@ -319,7 +319,9 @@ bool queueHealthCheck(std::unique_ptr<FDMultiplexer>& mplexer, const std::shared
 #endif
 
     if (!IsAnyAddress(ds->d_config.sourceAddr)) {
-      sock.setReuseAddr();
+      if (ds->doHealthcheckOverTCP()) {
+        sock.setReuseAddr();
+      }
 #ifdef IP_BIND_ADDRESS_NO_PORT
       if (ds->d_config.ipBindAddrNoPort) {
         SSetsockopt(sock.getHandle(), SOL_IP, IP_BIND_ADDRESS_NO_PORT, 1);