use mpls_ip_adjttl and mpls_ip6_adjttl in mpe instead of rolling it again.

mpls_ip_adjttl now patches the checksum rather than check it and
calculate it again. both mpls_ip_adjttl and mpls_ip6_adjttl now
rely on the caller to check the sysctls for whether they should run
or not, which paves the way for making it configurable in mpe via
the tunnel ioctls.

1 files changed, 7 insertions, 26 deletions

diff --git a/sys/net/if_mpe.c b/sys/net/if_mpe.c
index 1e556d96401..826cbdb1530 100644
--- a/sys/net/if_mpe.c
+++ b/sys/net/if_mpe.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: if_mpe.c,v 1.69 2019/01/27 04:54:06 dlg Exp $ */
+/* $OpenBSD: if_mpe.c,v 1.70 2019/01/27 05:13:04 dlg Exp $ */
 
 /*
  * Copyright (c) 2008 Pierre-Yves Ritschard <pyr@spootnik.org>
@@ -408,22 +408,9 @@ mpe_input(struct ifnet *ifp, struct mbuf *m)
 	switch (*mtod(n, uint8_t *) >> 4) {
 	case 4:
 		if (mpls_mapttl_ip) {
-			struct ip *ip;
-			uint16_t old, new, x;
-
-			if (m->m_len < sizeof(*ip)) {
-				m = m_pullup(m, sizeof(*ip));
-				if (m == NULL)
-					return;
-			}
-			ip = mtod(m, struct ip *);
-
-			old = htons(ip->ip_ttl << 8);
-			new = htons(ttl << 8);
-			x = ip->ip_sum + old - new;
-
-			ip->ip_ttl = ttl;
-			ip->ip_sum = (x) + (x >> 16);
+			m = mpls_ip_adjttl(m, ttl);
+			if (m == NULL)
+				return;
 		}
 		input = ipv4_input;
 		m->m_pkthdr.ph_family = AF_INET;
@@ -431,15 +418,9 @@ mpe_input(struct ifnet *ifp, struct mbuf *m)
 #ifdef INET6
 	case 6:
 		if (mpls_mapttl_ip6) {
-			struct ip6_hdr *ip6;
-
-			if (m->m_len < sizeof(*ip6)) {
-				m = m_pullup(m, sizeof(*ip6));
-				if (m == NULL)
-					return;
-			}
-			ip6 = mtod(m, struct ip6_hdr *);
-			ip6->ip6_hlim = ttl;
+			m = mpls_ip6_adjttl(m, ttl);
+			if (m == NULL)
+				return;
 		}
 		input = ipv6_input;
 		m->m_pkthdr.ph_family = AF_INET6;