From 29bb743c7c733974f132c35865ab43e8c0eed5c9 Mon Sep 17 00:00:00 2001
From: Otto Moerbeek <otto.moerbeek@open-xchange.com>
Date: Tue, 5 Mar 2019 16:30:22 +0100
Subject: [PATCH] Set IP(V6)_RECVERR socket option to get notified of more than
 just port unreachable errors on Linux.

See https://sourceware.org/bugzilla/show_bug.cgi?id=24047
---
 pdns/misc.cc          | 16 ++++++++++++++++
 pdns/misc.hh          |  1 +
 pdns/pdns_recursor.cc |  1 +
 3 files changed, 18 insertions(+)

diff --git a/pdns/misc.cc b/pdns/misc.cc
index b9863ed966..08c42251cf 100644
--- a/pdns/misc.cc
+++ b/pdns/misc.cc
@@ -1101,6 +1101,22 @@ bool isNonBlocking(int sock)
   return flags & O_NONBLOCK;
 }
 
+bool setReceiveSocketErrors(int sock, int af)
+{
+#ifdef __linux__
+  int tmp = 1, ret;
+  if (af == AF_INET) {
+    ret = setsockopt(sock, IPPROTO_IP, IP_RECVERR, &tmp, sizeof(tmp));
+  } else {
+    ret = setsockopt(sock, IPPROTO_IPV6, IPV6_RECVERR, &tmp, sizeof(tmp));
+  }
+  if (ret < 0) {
+    throw PDNSException(string("Setsockopt failed: ") + strerror(errno));
+  }
+#endif
+  return true;
+}
+
 // Closes a socket.
 int closesocket( int socket )
 {
diff --git a/pdns/misc.hh b/pdns/misc.hh
index f57a010bc6..9adfe35dc4 100644
--- a/pdns/misc.hh
+++ b/pdns/misc.hh
@@ -534,6 +534,7 @@ bool setNonBlocking( int sock );
 bool setTCPNoDelay(int sock);
 bool setReuseAddr(int sock);
 bool isNonBlocking(int sock);
+bool setReceiveSocketErrors(int sock, int af);
 int closesocket(int fd);
 bool setCloseOnExec(int sock);
 uint64_t udpErrorStats(const std::string& str);
diff --git a/pdns/pdns_recursor.cc b/pdns/pdns_recursor.cc
index 1a278125bf..dcbbf88579 100644
--- a/pdns/pdns_recursor.cc
+++ b/pdns/pdns_recursor.cc
@@ -623,6 +623,7 @@ public:
     if(!tries)
       throw PDNSException("Resolver binding to local query client socket on "+sin.toString()+": "+stringerror());
 
+    setReceiveSocketErrors(ret, family);
     setNonBlocking(ret);
     return ret;
   }
-- 
2.47.2