"source routing" in rpcbind

Fix a bug in rpcbind for multihomed hosts. If the server had interfaces on
two separate subnets, and a client on the first subnet contacted rpcbind at
the address on the second subnet, rpcbind would advertise addresses on the
first subnet. This is a bug, because it should prefer to advertise the
address where it was contacted. The requested service might be firewalled
off from the address on the first subnet, for example.

usr.sbin/rpcbind/check_bound.c
	If the address on which a request was received is known, pass that
	to addrmerge as the clnt_uaddr parameter. That is what addrmerge's
	comment indicates the parameter is supposed to mean. The previous
	behavior is that clnt_uaddr would contain the address from which the
	client sent the request.

usr.sbin/rpcbind/util.c
	Modify addrmerge to prefer to use an IP that is equal to clnt_uaddr,
	if one is found. Refactor the relevant portion of the function for
	clarity, and to reduce the number of ifdefs.

etc/mtree/BSD.tests.dist
usr.sbin/rpcbind/tests/Makefile
usr.sbin/rpcbind/tests/addrmerge_test.c
	Add unit tests for usr.sbin/rpcbind/util.c:addrmerge.

usr.sbin/rpcbind/check_bound.c
usr.sbin/rpcbind/rpcbind.h
usr.sbin/rpcbind/util.c
	Constify some function arguments

Reviewed by:	imp
MFC after:	4 weeks
Sponsored by:	Spectra Logic Corp
Differential Revision:	https://reviews.freebsd.org/D4690

1 files changed, 13 insertions, 2 deletions

diff --git a/usr.sbin/rpcbind/check_bound.c b/usr.sbin/rpcbind/check_bound.c
index 3691f5f..64b73c7 100644
--- a/usr.sbin/rpcbind/check_bound.c
+++ b/usr.sbin/rpcbind/check_bound.c
@@ -50,6 +50,7 @@ static	char sccsid[] = "@(#)check_bound.c 1.11 89/04/21 Copyr 1989 Sun Micro";
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <rpc/rpc.h>
+#include <rpc/svc_dg.h>
 #include <stdio.h>
 #include <netconfig.h>
 #include <syslog.h>
@@ -159,6 +160,7 @@ char *
 mergeaddr(SVCXPRT *xprt, char *netid, char *uaddr, char *saddr)
 {
 	struct fdlist *fdl;
+	struct svc_dg_data *dg_data;
 	char *c_uaddr, *s_uaddr, *m_uaddr, *allocated_uaddr = NULL;
 
 	for (fdl = fdhead; fdl; fdl = fdl->next)
@@ -170,11 +172,20 @@ mergeaddr(SVCXPRT *xprt, char *netid, char *uaddr, char *saddr)
 		/* that server died */
 		return (nullstring);
 	/*
+	 * Try to determine the local address on which the client contacted us,
+	 * so we can send a reply from the same address.  If it's unknown, then
+	 * try to determine which address the client used, and pick a nearby
+	 * local address.
+	 *
 	 * If saddr is not NULL, the remote client may have included the
 	 * address by which it contacted us.  Use that for the "client" uaddr,
 	 * otherwise use the info from the SVCXPRT.
 	 */
-	if (saddr != NULL) {
+	dg_data = (struct svc_dg_data*)xprt->xp_p2;
+	if (dg_data != NULL && dg_data->su_srcaddr.buf != NULL) {
+		c_uaddr = taddr2uaddr(fdl->nconf, &dg_data->su_srcaddr);
+	}
+	else if (saddr != NULL) {
 		c_uaddr = saddr;
 	} else {
 		c_uaddr = taddr2uaddr(fdl->nconf, svc_getrpccaller(xprt));
@@ -217,7 +228,7 @@ mergeaddr(SVCXPRT *xprt, char *netid, char *uaddr, char *saddr)
  * structure should not be freed.
  */
 struct netconfig *
-rpcbind_get_conf(char *netid)
+rpcbind_get_conf(const char *netid)
 {
 	struct fdlist *fdl;