Bug 225792

Summary: ECMP is broken since tryforward()
Product: Base System Reporter: Olivier Cochard <olivier>
Component: kernAssignee: Alexander V. Chernikov <melifaro>
Status: Open ---    
Severity: Affects Some People CC: ae, crest, dch, emaste, koobs, melifaro, moremore2, seb+freebsd
Priority: --- Keywords: regression
Version: 11.0-STABLEFlags: koobs: mfc-stable12?
koobs: mfc-stable11?
Hardware: Any   
OS: Any   
Description Flags
add radix_mpath.h back none

Description Olivier Cochard freebsd_committer 2018-02-09 16:25:42 UTC
For the record: As mentioned into the mailing-list [1], adding "options RADIX_MPATH" doesn't allow any more to use ECMP.
The new ip_tryforward (like the previous fastforward) didn't support ECMP: a FreeBSD router sticks to its first route entry and never try the second entry.

[1] https://lists.freebsd.org/pipermail/freebsd-net/2017-February/047203.html
Comment 1 Kubilay Kocak freebsd_committer freebsd_triage 2019-08-23 03:51:40 UTC
Created attachment 206809 [details]

@Olivier I assume this is still an issue in stable/11,12 and CURRENT, can you confirm?

^Triage: Attach patch from Ermal (eri@) on the mailing list thread, which may (likely?) need a re-base against latest CURRENT
Comment 2 Kubilay Kocak freebsd_committer freebsd_triage 2019-08-23 03:52:59 UTC
Add ae@ to CC as they mentioned some code would need to be written (which was), in case they can assist with review
Comment 3 Olivier Cochard freebsd_committer 2019-08-23 07:07:28 UTC
(In reply to Kubilay Kocak from comment #1)

Yes this is still in issue on stable/11/12/current.
Comment 4 Simon K. 2019-11-01 01:39:49 UTC
Created attachment 208751 [details]
add radix_mpath.h back

   IPSEC policy or set sendredirect to "1" would disable tryforward(). Then the packet will fall into the slowpath. AKA. normal ip_input process. But ip_input.c missed some .h files, eg. radix_mpath.h, then ECMP is broken.
   Set sendredirect to "1" is not a good idea for a router, so I add "fastforwarding" back. Now you can set it to "0" to disable fastpath.
   The attached patch I've tested on FB12-stable r354079 is passed.