Bug #6868: Interface MTU Setting not applied to all IPv6 routes - pfSense - pfSense bugtracker

Actions

Copy link

Bug #6868

closed

Interface MTU Setting not applied to all IPv6 routes

Added by Daryl Morse about 8 years ago. Updated over 4 years ago.

Status:

Resolved

Priority:

Normal

Assignee:

Luiz Souza

Category:

Interfaces

Target version:

2.5.0

Start date:

10/20/2016

Due date:

% Done:

100%

Estimated time:

Plus Target Version:

Release Notes:

Affected Version:

All

Affected Architecture:

Description

Running 2.3.2_1 using an HE/64 tunnel. Adjusting MTU to troubleshoot possible PMTUD problem. Found that setting for MTU in Interfaces / OPT1 only changes MTU for default route, but not for other gif0 routes. MTU of 1280 is applied to other routes.

default 2001:abc:c:1111::1 (MTU changed by OPT1 setting)
2001:abc:c:111::1 link#7 (MTU not changed)
fe80::%gif0/64 link#7 (MTU not changed)
ff01::%gif0/32 2001:abc:c:1111::2 (MTU not changed)
ff01::%gif0/32 2001:abc:c:1111::2 (MTU not changed)

Used command prompt route -6 change <route> -mtu 1480 to change MTU. After disabling OPT1 and enabling OPT1, MTU reset back to 1280.

Actions

Copy link

Updated by Jim Thompson about 8 years ago

Assignee set to Jim Pingle

assigned to Pingle for analysis.

Actions

Copy link

Updated by Jim Pingle about 8 years ago

Subject changed from MTU Setting in for OPT1 Interface not applied to all gif0 routes to Interface MTU Setting not applied to all IPv6 routes
Category set to Interfaces
Status changed from New to Confirmed
Assignee deleted (~~Jim Pingle~~)
Target version set to 2.4.0
Affected Version set to All

I can reproduce the behavior on 2.3.x. If I adjust the MTU of an assigned interface, only the default and/or link route for IPv6 on the interface has its MTU adjusted, not others.

If I attempt the same thing on an IPv4 interface, the MTU for all routes is adjusted.

This does not appear to be specific to GIF, but to IPv6 in general. If I change the MTU on LAN, for example, the link route MTUs lower but none of the link-local routes do:

: netstat -rWn | grep vmx1
10.163.0.0/24      link#2             U             0   1350       vmx1
2001:470:xxxx:xxxx::/64           link#2                        U             0   1350     vmx1
fe80::%vmx1/64                    link#2                        U             0   1500     vmx1
fe80::20c:29ff:xxxx:42f6%vmx1     link#2                        UHS           0  16384      lo0
ff01::%vmx1/32                    fe80::20c:29ff:xxxx:42f6%vmx1 U             0   1500     vmx1
ff02::%vmx1/32                    fe80::20c:29ff:xxxx:42f6%vmx1 U             0   1500     vmx1

And the same on WAN (which doesn't have V6, but has multiple V4 routes):

default            xxx.xxx.xxx.161    UGS           4   1450       vmx0
xxx.xxx.xxx.160/28 link#1             U             6   1450       vmx0
xxx.xxx.253.14     xxx.xxx.xxx.161    UGHS         13   1450       vmx0
fe80::%vmx0/64                    link#1                        U             0   1500     vmx0
fe80::20c:29ff:xxxx:42ec%vmx0     link#1                        UHS           0  16384      lo0
ff01::%vmx0/32                    fe80::20c:29ff:xxxx:42ec%vmx0 U             0   1500     vmx0
ff02::%vmx0/32                    fe80::20c:29ff:xxxx:42ec%vmx0 U             0   1500     vmx0

We have had some issues setting MTU in the past (e.g. #4397, #5842, #2674), but none appear to exactly match this.

Attempting to reproduce the same issue on 2.4 has better but not perfect results. The link-local routes are updated with the correct MTU, but host and static routes are not.

If I manually set the MTU on an interface in stock FreeBSD 11, all link-local and static routes get an updated MTU.

Actions

Copy link