[src/trunk]: src/sys/netinet6 Tidy up ip6_getpmtu

[ozaki-r <ozaki-r%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/ff9ce3412c32
branches:  trunk
changeset: 818917:ff9ce3412c32
user:      ozaki-r <ozaki-r%NetBSD.org@localhost>
date:      Mon Nov 07 01:05:39 2016 +0000

description:
Tidy up ip6_getpmtu

Pull rtcache thing out of ip6_getpmtu; that isn't an essential
of the function. Add comments inspired by FreeBSD.

No functional change.

diffstat:

 sys/netinet6/ip6_output.c |  55 +++++++++++++++++++++++++++-------------------
 1 files changed, 32 insertions(+), 23 deletions(-)

diffs (116 lines):

diff -r a65021836358 -r ff9ce3412c32 sys/netinet6/ip6_output.c
--- a/sys/netinet6/ip6_output.c Mon Nov 07 00:54:48 2016 +0000
+++ b/sys/netinet6/ip6_output.c Mon Nov 07 01:05:39 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: ip6_output.c,v 1.175 2016/09/20 14:30:13 roy Exp $     */
+/*     $NetBSD: ip6_output.c,v 1.176 2016/11/07 01:05:39 ozaki-r Exp $ */
 /*     $KAME: ip6_output.c,v 1.172 2001/03/25 09:55:56 itojun Exp $    */
 
 /*
@@ -62,7 +62,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ip6_output.c,v 1.175 2016/09/20 14:30:13 roy Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ip6_output.c,v 1.176 2016/11/07 01:05:39 ozaki-r Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_inet.h"
@@ -133,8 +133,7 @@
        struct ip6_frag **);
 static int ip6_insert_jumboopt(struct ip6_exthdrs *, u_int32_t);
 static int ip6_splithdr(struct mbuf *, struct ip6_exthdrs *);
-static int ip6_getpmtu(struct route *, struct route *, struct ifnet *,
-    const struct in6_addr *, u_long *, int *);
+static int ip6_getpmtu(struct rtentry *, struct ifnet *, u_long *, int *);
 static int copypktopts(struct ip6_pktopts *, struct ip6_pktopts *, int);
 static int ip6_ifaddrvalid(const struct in6_addr *);
 
@@ -170,7 +169,7 @@
        int hlen, tlen, len, off;
        bool tso;
        struct route ip6route;
-       struct rtentry *rt = NULL;
+       struct rtentry *rt = NULL, *rt_pmtu;
        const struct sockaddr_in6 *dst;
        struct sockaddr_in6 src_sa, dst_sa;
        int error = 0;
@@ -661,8 +660,24 @@
                *ifpp = ifp;
 
        /* Determine path MTU. */
-       if ((error = ip6_getpmtu(ro_pmtu, ro, ifp, &finaldst, &mtu,
-           &alwaysfrag)) != 0)
+       /*
+        * ro_pmtu represent final destination while
+        * ro might represent immediate destination.
+        * Use ro_pmtu destination since MTU might differ.
+        */
+       if (ro_pmtu != ro) {
+               union {
+                       struct sockaddr         dst;
+                       struct sockaddr_in6     dst6;
+               } u;
+
+               /* ro_pmtu may not have a cache */
+               sockaddr_in6_init(&u.dst6, &finaldst, 0, 0, 0);
+               rt_pmtu = rtcache_lookup(ro_pmtu, &u.dst);
+       } else
+               rt_pmtu = rtcache_validate(ro_pmtu);
+       error = ip6_getpmtu(rt_pmtu, ifp, &mtu, &alwaysfrag);
+       if (error != 0)
                goto bad;
 
        /*
@@ -1232,25 +1247,13 @@
 }
 
 static int
-ip6_getpmtu(struct route *ro_pmtu, struct route *ro, struct ifnet *ifp,
-    const struct in6_addr *dst, u_long *mtup, int *alwaysfragp)
+ip6_getpmtu(struct rtentry *rt, struct ifnet *ifp, u_long *mtup,
+    int *alwaysfragp)
 {
-       struct rtentry *rt;
        u_int32_t mtu = 0;
        int alwaysfrag = 0;
        int error = 0;
 
-       if (ro_pmtu != ro) {
-               union {
-                       struct sockaddr         dst;
-                       struct sockaddr_in6     dst6;
-               } u;
-
-               /* The first hop and the final destination may differ. */
-               sockaddr_in6_init(&u.dst6, dst, 0, 0, 0);
-               rt = rtcache_lookup(ro_pmtu, &u.dst);
-       } else
-               rt = rtcache_validate(ro_pmtu);
        if (rt != NULL) {
                u_int32_t ifmtu;
 
@@ -1830,6 +1833,11 @@
                        u_long pmtu = 0;
                        struct ip6_mtuinfo mtuinfo;
                        struct route *ro = &in6p->in6p_route;
+                       struct rtentry *rt;
+                       union {
+                               struct sockaddr         dst;
+                               struct sockaddr_in6     dst6;
+                       } u;
 
                        if (!(so->so_state & SS_ISCONNECTED))
                                return (ENOTCONN);
@@ -1838,8 +1846,9 @@
                         * routing, or optional information to specify
                         * the outgoing interface.
                         */
-                       error = ip6_getpmtu(ro, NULL, NULL,
-                           &in6p->in6p_faddr, &pmtu, NULL);
+                       sockaddr_in6_init(&u.dst6, &in6p->in6p_faddr, 0, 0, 0);
+                       rt = rtcache_lookup(ro, &u.dst);
+                       error = ip6_getpmtu(rt, NULL, &pmtu, NULL);
                        if (error)
                                break;
                        if (pmtu > IPV6_MAXPACKET)