some interfaces could support copying the ttl from an inner packet to an outer
one, but there's no obvious way to configure that at the moment.
this borrows the semantic of using -1 for a special thing from
vnetid. this could let you go "ifconfig gre0 ttl copy" to enable
it. this also changes ifconfig to show copy if the value is -1. eg,
mobileip implicitly copies ttl, so it's output would be:
mobileip0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1488
index 8 priority 0 llprio 3
groups: mobileip
tunnel: inet 192.168.96.40 -> 192.168.96.54 ttl copy
inet 100.64.2.2 --> 100.64.2.1 netmask 0xffffffff
this makes a point of not touching ttl 0. the validity of ttl 0 is
a discussion for another time.
ok?
Index: ifconfig.c
===================================================================
RCS file: /cvs/src/sbin/ifconfig/ifconfig.c,v
retrieving revision 1.353
diff -u -p -r1.353 ifconfig.c
--- ifconfig.c 16 Jan 2018 10:33:55 -0000 1.353
+++ ifconfig.c 8 Feb 2018 06:03:14 -0000
@@ -2738,8 +2733,12 @@ phys_status(int force)
if (dstport)
printf(":%u", ntohs(dstport));
- if (ioctl(s, SIOCGLIFPHYTTL, (caddr_t)&ifr) == 0 && ifr.ifr_ttl > 0)
- printf(" ttl %d", ifr.ifr_ttl);
+ if (ioctl(s, SIOCGLIFPHYTTL, (caddr_t)&ifr) == 0) {
+ if (ifr.ifr_ttl == -1)
+ printf(" ttl copy");
+ else if (ifr.ifr_ttl > 0)
+ printf(" ttl %d", ifr.ifr_ttl);
+ }
#ifndef SMALL
if (ioctl(s, SIOCGLIFPHYRTABLE, (caddr_t)&ifr) == 0 &&
(rdomainid != 0 || ifr.ifr_rdomainid != 0))
@@ -3261,9 +3260,13 @@ settunnelttl(const char *id, int param)
const char *errmsg = NULL;
int ttl;
- ttl = strtonum(id, 0, 0xff, &errmsg);
- if (errmsg)
- errx(1, "tunnelttl %s: %s", id, errmsg);
+ if (strcmp(id, "copy") == 0)
+ ttl = -1;
+ else {
+ ttl = strtonum(id, 0, 0xff, &errmsg);
+ if (errmsg)
+ errx(1, "tunnelttl %s: %s", id, errmsg);
+ }
strlcpy(ifr.ifr_name, name, sizeof(ifr.ifr_name));
ifr.ifr_ttl = ttl;
