[src/trunk]: src/sys/netinet6 Try to sound a little less pessimistic, there i...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/1b882769ac63
branches:  trunk
changeset: 359131:1b882769ac63
user:      maxv <maxv%NetBSD.org@localhost>
date:      Wed Jan 31 14:10:11 2018 +0000

description:
Try to sound a little less pessimistic, there is nothing wrong here.

diffstat:

 sys/netinet6/ip6_output.c |  28 +++++++++++++++-------------
 1 files changed, 15 insertions(+), 13 deletions(-)

diffs (81 lines):

diff -r 0c6571a00b7f -r 1b882769ac63 sys/netinet6/ip6_output.c
--- a/sys/netinet6/ip6_output.c Wed Jan 31 13:57:08 2018 +0000
+++ b/sys/netinet6/ip6_output.c Wed Jan 31 14:10:11 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: ip6_output.c,v 1.197 2018/01/31 13:57:08 maxv Exp $    */
+/*     $NetBSD: ip6_output.c,v 1.198 2018/01/31 14:10:11 maxv 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 1.197 2018/01/31 13:57:08 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ip6_output.c,v 1.198 2018/01/31 14:10:11 maxv Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_inet.h"
@@ -1164,7 +1164,7 @@
         * jumbo payload option, allocate a cluster to store the whole options.
         * Otherwise, use it to store the options.
         */
-       if (exthdrs->ip6e_hbh == 0) {
+       if (exthdrs->ip6e_hbh == NULL) {
                MGET(mopt, M_DONTWAIT, MT_DATA);
                if (mopt == 0)
                        return (ENOBUFS);
@@ -1177,25 +1177,26 @@
 
                mopt = exthdrs->ip6e_hbh;
                if (M_TRAILINGSPACE(mopt) < JUMBOOPTLEN) {
+                       const int oldoptlen = mopt->m_len;
+                       struct mbuf *n;
+
                        /*
-                        * XXX assumption:
+                        * Assumptions:
                         * - exthdrs->ip6e_hbh is not referenced from places
                         *   other than exthdrs.
                         * - exthdrs->ip6e_hbh is not an mbuf chain.
                         */
-                       int oldoptlen = mopt->m_len;
-                       struct mbuf *n;
+                       KASSERT(mopt->m_next == NULL);
 
                        /*
-                        * XXX: give up if the whole (new) hbh header does
-                        * not fit even in an mbuf cluster.
+                        * Give up if the whole (new) hbh header does not fit
+                        * even in an mbuf cluster.
                         */
                        if (oldoptlen + JUMBOOPTLEN > MCLBYTES)
-                               return (ENOBUFS);
+                               return ENOBUFS;
 
                        /*
-                        * As a consequence, we must always prepare a cluster
-                        * at this point.
+                        * At this point, we must always prepare a cluster.
                         */
                        MGET(n, M_DONTWAIT, MT_DATA);
                        if (n) {
@@ -1206,7 +1207,8 @@
                                }
                        }
                        if (!n)
-                               return (ENOBUFS);
+                               return ENOBUFS;
+
                        n->m_len = oldoptlen + JUMBOOPTLEN;
                        bcopy(mtod(mopt, void *), mtod(n, void *),
                            oldoptlen);
@@ -1237,7 +1239,7 @@
        /* finally, adjust the packet header length */
        exthdrs->ip6e_ip6->m_pkthdr.len += JUMBOOPTLEN;
 
-       return (0);
+       return 0;
 #undef JUMBOOPTLEN
 }