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Bug #11409

IPv4 MSS value is incorrectly applied to IPv6 packets

Added by Michael Smith 2 months ago. Updated 5 days ago.

Status:
Closed
Priority:
Normal
Assignee:
Category:
Interfaces
Target version:
Start date:
02/12/2021
Due date:
% Done:

100%

Estimated time:
Affected Version:
2.4.5-p1
Affected Architecture:
All
Release Notes:
Default

Description

Follows from discussion at https://forum.netgate.com/topic/152935/ipv6-pppoe-mss-incorrect/.

When setting up MSS clamping on the WAN interface, the calculation applied on the entered value subtracts a hard-coded constant of 40 bytes, assuming 20 bytes for TCP and 20 bytes for IPv4. This is also applied on IPv6 packets, when the calculation in that case should be 20 bytes for TCP and 40 bytes for IPV6. This is done on line 640 of /src/etc/inc/filter.inc (https://github.com/pfsense/pfsense/blob/11fd7da72502c991b1f1c0e886ea212235f4a505/src/etc/inc/filter.inc#L640).

Thus, an end user who needs to set MSS can only do so by entering a value that works for IPv4 or IPv6, and not both. For example, in my setup with a PPPoE connection, I must enter 1472 as MSS instead of the correct value of 1492 to have MSS work over IPv6.

Associated revisions

Revision 1d378c4e (diff)
Added by Viktor Gurov about 2 months ago

Set correct TCP MSS for IPv6. Fixes #11409

Revision d49dd060 (diff)
Added by Viktor Gurov about 1 month ago

Set correct TCP MSS for IPv6. Fixes #11409

(cherry picked from commit 1d378c4ec6c440dabffba41bf5e4ef291acb9aa2)

History

#2 Updated by Jim Pingle 2 months ago

  • Status changed from New to Pull Request Review
  • Target version set to CE-Next

#3 Updated by Renato Botelho about 2 months ago

  • Status changed from Pull Request Review to Feedback
  • Assignee set to Viktor Gurov

PR has been merged. Thanks!

#4 Updated by Viktor Gurov about 2 months ago

  • % Done changed from 0 to 100

#5 Updated by Jim Pingle about 1 month ago

  • Status changed from Feedback to Waiting on Merge
  • Target version changed from CE-Next to 2.5.1

#6 Updated by Renato Botelho about 1 month ago

  • Status changed from Waiting on Merge to Feedback

Cherry-picked to RELENG_2_5_1

#7 Updated by Jim Pingle about 1 month ago

  • Subject changed from src/etc/inc/filter.inc: IPv4 MSS incorrectly applied to IPv6 packets to IPv4 MSS value is incorrectly applied to IPv6 packets

Updating subject for release notes.

#8 Updated by Jim Pingle 5 days ago

  • Status changed from Feedback to Closed

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