git: 2756774c3f53 - main - netinet6: simplify selectroute()

The branch main has been updated by melifaro:

URL: https://cgit.FreeBSD.org/src/commit/?id=2756774c3f537bc566362ef424d992092fb6fc87

commit 2756774c3f537bc566362ef424d992092fb6fc87
Author:     Alexander V. Chernikov <melifaro@FreeBSD.org>
AuthorDate: 2022-07-04 18:05:38 +0000
Commit:     Alexander V. Chernikov <melifaro@FreeBSD.org>
CommitDate: 2022-07-08 11:27:16 +0000

    netinet6: simplify selectroute()
    
    Effectively selectroute() addresses two different cases:
     providing interface info for multicast destinations and providing
     nexthop data for unicast ones. Current implementation intertwines
     handling of both cases, especially in the error handling part.
    Factor out all route lookup logic in a separate function,
     lookup_route() to simplify the code.
    Ensure consistent KPI: no error means *retifp is set and otherwise.
    
    Differential Revision: https://reviews.freebsd.org/D35711
    MFC after:      2 weeks
---
 sys/netinet6/in6_src.c | 115 ++++++++++++++++++++++++-------------------------
 1 file changed, 56 insertions(+), 59 deletions(-)

diff --git a/sys/netinet6/in6_src.c b/sys/netinet6/in6_src.c
index e44a1b0873b4..7188282013cc 100644
--- a/sys/netinet6/in6_src.c
+++ b/sys/netinet6/in6_src.c
@@ -643,6 +643,47 @@ cache_route(uint32_t fibnum, const struct sockaddr_in6 *dst, struct route_in6 *r
 	return (ro->ro_nh);
 }
 
+static struct nhop_object *
+lookup_route(uint32_t fibnum, struct sockaddr_in6 *dst, struct route_in6 *ro,
+    struct ip6_pktopts *opts, uint32_t flowid)
+{
+	struct nhop_object *nh = NULL;
+
+	/*
+	 * If the next hop address for the packet is specified by the caller,
+	 * use it as the gateway.
+	 */
+	if (opts && opts->ip6po_nexthop) {
+		struct route_in6 *ron = &opts->ip6po_nextroute;
+		struct sockaddr_in6 *sin6_next = satosin6(opts->ip6po_nexthop);
+
+		nh = cache_route(fibnum, sin6_next, ron, flowid);
+
+		/*
+		 * The node identified by that address must be a
+		 * neighbor of the sending host.
+		 */
+		if (nh != NULL && (nh->nh_flags & NHF_GATEWAY) != 0)
+			nh = NULL;
+	} else if (ro != NULL) {
+		nh = cache_route(fibnum, dst, ro, flowid);
+		if (nh == NULL)
+			return (NULL);
+
+		/*
+		 * Check if the outgoing interface conflicts with
+		 * the interface specified by ipi6_ifindex (if specified).
+		 */
+		struct in6_pktinfo *pi;
+		if (opts && (pi = opts->ip6po_pktinfo) != NULL && pi->ipi6_ifindex) {
+			if (nh->nh_aifp->if_index != pi->ipi6_ifindex)
+				nh = NULL;
+		}
+	}
+
+	return (nh);
+}
+
 /*
  * Finds outgoing nexthop or the outgoing interface for the
  * @dstsock.
@@ -656,11 +697,8 @@ selectroute(struct sockaddr_in6 *dstsock, struct ip6_pktopts *opts,
 {
 	int error = 0;
 	struct ifnet *ifp = NULL;
-	struct nhop_object *nh = NULL;
-	struct sockaddr_in6 *sin6_next;
 	struct in6_pktinfo *pi = NULL;
 	struct in6_addr *dst = &dstsock->sin6_addr;
-	uint32_t zoneid;
 
 	/* If the caller specify the outgoing interface explicitly, use it. */
 	if (opts && (pi = opts->ip6po_pktinfo) != NULL && pi->ipi6_ifindex) {
@@ -689,66 +727,28 @@ selectroute(struct sockaddr_in6 *dstsock, struct ip6_pktopts *opts,
 	 */
 	if (IN6_IS_ADDR_MC_LINKLOCAL(dst) ||
 	    IN6_IS_ADDR_MC_NODELOCAL(dst)) {
-		zoneid = ntohs(in6_getscope(dst));
+		uint32_t zoneid = ntohs(in6_getscope(dst));
 		if (zoneid > 0) {
 			ifp = in6_getlinkifnet(zoneid);
 			goto done;
 		}
 	}
 
-  getroute:
-	/*
-	 * If the next hop address for the packet is specified by the caller,
-	 * use it as the gateway.
-	 */
-	if (opts && opts->ip6po_nexthop) {
-		struct route_in6 *ron = &opts->ip6po_nextroute;
-		sin6_next = satosin6(opts->ip6po_nexthop);
-
-		nh = cache_route(fibnum, sin6_next, ron, flowid);
-
-		/*
-		 * The node identified by that address must be a
-		 * neighbor of the sending host.
-		 */
-		if (nh != NULL && (nh->nh_flags & NHF_GATEWAY) == 0)
-			ifp = nh->nh_ifp;
-		else {
-			nh = NULL; // cached nh is still stored in @opts
-			error = EHOSTUNREACH;
-		}
-	} else if (ro != NULL) {
-		nh = cache_route(fibnum, dstsock, ro, flowid);
-		if (nh != NULL)
-			ifp = nh->nh_ifp;
-		else
-			error = EHOSTUNREACH;
-
-		/*
-		 * Check if the outgoing interface conflicts with
-		 * the interface specified by ipi6_ifindex (if specified).
-		 * Note that loopback interface is always okay.
-		 * (this may happen when we are sending a packet to one of
-		 *  our own addresses.)
-		 */
-		if (ifp && opts && opts->ip6po_pktinfo &&
-		    opts->ip6po_pktinfo->ipi6_ifindex) {
-			if (!(ifp->if_flags & IFF_LOOPBACK) &&
-			    ifp->if_index !=
-			    opts->ip6po_pktinfo->ipi6_ifindex) {
-				error = EHOSTUNREACH;
-				ifp = NULL;
-				nh = NULL;
-			}
-		}
+  getroute:;
+	struct nhop_object *nh = lookup_route(fibnum, dstsock, ro, opts, flowid);
+	if (nh != NULL) {
+		*retifp = nh->nh_aifp;
+		error = 0;
+	} else {
+		*retifp = NULL;
+		IP6STAT_INC(ip6s_noroute);
+		error = EHOSTUNREACH;
 	}
-	/*
-	 * Output must be consistent: no error -> both ifp and nh != NULL,
-	 * otherwise both NULL
-	 */
+	*retnh = nh;
+	return (error);
 
   done:
-	if (ifp == NULL && nh == NULL) {
+	if (ifp == NULL) {
 		/*
 		 * This can happen if the caller did not pass a cached route
 		 * nor any other hints.  We treat this case an error.
@@ -758,11 +758,8 @@ selectroute(struct sockaddr_in6 *dstsock, struct ip6_pktopts *opts,
 	if (error == EHOSTUNREACH)
 		IP6STAT_INC(ip6s_noroute);
 
-	if (nh != NULL)
-		*retifp = nh->nh_aifp;
-	else
-		*retifp = ifp;
-	*retnh = nh;	/* nh may be NULL */
+	*retifp = ifp;
+	*retnh = NULL;
 
 	return (error);
 }