From c2e80cf47ebb1ceecb4ad2ee01191ba2677f6fee Mon Sep 17 00:00:00 2001
From: Mark Andrews <marka@isc.org>
Date: Thu, 1 Nov 2012 08:42:56 +1100
Subject: [PATCH] 3411.   [tuning]        Use IPV6_USE_MIN_MTU or equivalent
 with TCP in addition                         to UDP. [RT #31690]

Squashed commit of the following:

commit bcbe9ae7a99e1f7f4236a22739a793b51ace8684
Author: Mark Andrews <marka@isc.org>
Date:   Wed Oct 31 15:10:53 2012 +1100

    Use IPV6_USE_MIN_MTU for TCP as well as UDP
---
 CHANGES                |  3 +++
 lib/isc/unix/socket.c  | 60 +++++++++++++++++++++++-------------------
 lib/isc/win32/socket.c | 29 ++++++++++++++------
 3 files changed, 57 insertions(+), 35 deletions(-)

diff --git a/CHANGES b/CHANGES
index 9ea3a70191..becaa95aed 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,6 @@
+3411.	[tuning]	Use IPV6_USE_MIN_MTU or equivalent with TCP in addition
+			to UDP. [RT #31690]
+
 3410.	[bug]		Addressed Coverity warnings. [RT #31626]
 
 3409.	[contrib]	contrib/dane/mkdane.sh: Tool to generate TLSA RR's
diff --git a/lib/isc/unix/socket.c b/lib/isc/unix/socket.c
index ffe7e02f5f..794374ee61 100644
--- a/lib/isc/unix/socket.c
+++ b/lib/isc/unix/socket.c
@@ -2262,6 +2262,28 @@ clear_bsdcompat(void) {
 }
 #endif
 
+static void
+use_min_mtu(isc__socket_t *sock) {
+#ifdef IPV6_USE_MIN_MTU
+	/* use minimum MTU */
+	if (sock->pf == AF_INET6) {
+		int on = 1;
+		(void)setsockopt(sock->fd, IPPROTO_IPV6, IPV6_USE_MIN_MTU,
+			        (void *)&on, sizeof(on));
+	}
+#endif
+#if defined(IPV6_MTU)
+	/*
+	 * Use minimum MTU on IPv6 sockets.
+	 */
+	if (sock->pf == AF_INET6) {
+		int mtu = 1280;
+		(void)setsockopt(sock->fd, IPPROTO_IPV6, IPV6_MTU,
+				 &mtu, sizeof(mtu));
+	}
+#endif
+}
+
 static isc_result_t
 opensocket(isc__socketmgr_t *manager, isc__socket_t *sock,
 	   isc__socket_t *dup_socket)
@@ -2270,7 +2292,7 @@ opensocket(isc__socketmgr_t *manager, isc__socket_t *sock,
 	char strbuf[ISC_STRERRORSIZE];
 	const char *err = "socket";
 	int tries = 0;
-#if defined(USE_CMSG) || defined(SO_BSDCOMPAT)
+#if defined(USE_CMSG) || defined(SO_BSDCOMPAT) || defined(SO_NOSIGPIPE)
 	int on = 1;
 #endif
 #if defined(SO_RCVBUF)
@@ -2426,6 +2448,11 @@ opensocket(isc__socketmgr_t *manager, isc__socket_t *sock,
 	}
 #endif
 
+	/*
+	 * Use minimum mtu if possible.
+	 */
+	use_min_mtu(sock);
+
 #if defined(USE_CMSG) || defined(SO_RCVBUF)
 	if (sock->type == isc_sockettype_udp) {
 
@@ -2490,32 +2517,6 @@ opensocket(isc__socketmgr_t *manager, isc__socket_t *sock,
 		}
 #endif /* IPV6_RECVPKTINFO */
 #endif /* ISC_PLATFORM_HAVEIN6PKTINFO */
-#ifdef IPV6_USE_MIN_MTU        /* RFC 3542, not too common yet*/
-		/* use minimum MTU */
-		if (sock->pf == AF_INET6 &&
-		    setsockopt(sock->fd, IPPROTO_IPV6, IPV6_USE_MIN_MTU,
-			       (void *)&on, sizeof(on)) < 0) {
-			isc__strerror(errno, strbuf, sizeof(strbuf));
-			UNEXPECTED_ERROR(__FILE__, __LINE__,
-					 "setsockopt(%d, IPV6_USE_MIN_MTU) "
-					 "%s: %s", sock->fd,
-					 isc_msgcat_get(isc_msgcat,
-							ISC_MSGSET_GENERAL,
-							ISC_MSG_FAILED,
-							"failed"),
-					 strbuf);
-		}
-#endif
-#if defined(IPV6_MTU)
-		/*
-		 * Use minimum MTU on IPv6 sockets.
-		 */
-		if (sock->pf == AF_INET6) {
-			int mtu = 1280;
-			(void)setsockopt(sock->fd, IPPROTO_IPV6, IPV6_MTU,
-					 &mtu, sizeof(mtu));
-		}
-#endif
 #if defined(IPV6_MTU_DISCOVER) && defined(IPV6_PMTUDISC_DONT)
 		/*
 		 * Turn off Path MTU discovery on IPv6/UDP sockets.
@@ -3312,6 +3313,11 @@ internal_accept(isc_task_t *me, isc_event_t *ev) {
 		NEWCONNSOCK(dev)->bound = 1;
 		NEWCONNSOCK(dev)->connected = 1;
 
+		/*
+		 * Use minimum mtu if possible.
+		 */
+		use_min_mtu(NEWCONNSOCK(dev));
+
 		/*
 		 * Save away the remote address
 		 */
diff --git a/lib/isc/win32/socket.c b/lib/isc/win32/socket.c
index ffcefb0606..1803de4f7b 100644
--- a/lib/isc/win32/socket.c
+++ b/lib/isc/win32/socket.c
@@ -1431,6 +1431,18 @@ startio_send(isc_socket_t *sock, isc_socketevent_t *dev, int *nbytes,
 	return (status);
 }
 
+static void
+use_min_mtu(isc__socket_t *sock) {
+#ifdef IPV6_USE_MIN_MTU
+	/* use minimum MTU */
+	if (sock->pf == AF_INET6) {
+		int on = 1;
+		(void)setsockopt(sock->fd, IPPROTO_IPV6, IPV6_USE_MIN_MTU,
+			        (void *)&on, sizeof(on));
+	}
+#endif
+}
+
 static isc_result_t
 allocate_socket(isc_socketmgr_t *manager, isc_sockettype_t type,
 		isc_socket_t **socketp) {
@@ -1737,6 +1749,10 @@ socket_create(isc_socketmgr_t *manager, int pf, isc_sockettype_t type,
 		return (result);
 	}
 
+	/*
+	 * Use minimum mtu if possible.
+	 */
+	use_min_mtu(sock);
 
 #if defined(USE_CMSG) || defined(SO_RCVBUF)
 	if (type == isc_sockettype_udp) {
@@ -1774,14 +1790,6 @@ socket_create(isc_socketmgr_t *manager, int pf, isc_sockettype_t type,
 					 strbuf);
 		}
 #endif /* IPV6_RECVPKTINFO */
-#ifdef IPV6_USE_MIN_MTU	/*2292bis, not too common yet*/
-		/* use minimum MTU */
-		if (pf == AF_INET6) {
-			(void)setsockopt(sock->fd, IPPROTO_IPV6,
-					 IPV6_USE_MIN_MTU,
-					 (char *)&on, sizeof(on));
-		}
-#endif
 #endif /* ISC_PLATFORM_HAVEIPV6 */
 #endif /* defined(USE_CMSG) */
 
@@ -2068,6 +2076,11 @@ internal_accept(isc_socket_t *sock, IoCompletionInfo *lpo, int accept_errno) {
 	result = make_nonblock(adev->newsocket->fd);
 	INSIST(result == ISC_R_SUCCESS);
 
+	/*
+	 * Use minimum mtu if possible.
+	 */
+	use_min_mtu(adev->newsocket);
+
 	INSIST(setsockopt(nsock->fd, SOL_SOCKET, SO_UPDATE_ACCEPT_CONTEXT,
 			  (char *)&sock->fd, sizeof(sock->fd)) == 0);