Bug 253620

Summary:	Calling route delete with an invalid gateway deletes the route
Product:	Base System	Reporter:	Lomash Gupta <lgupta>
Component:	kern	Assignee:	freebsd-net (Nobody) <net>
Status:	New ---
Severity:	Affects Many People	CC:	emaste, ghuckriede, melifaro
Priority:	---
Version:	12.2-RELEASE
Hardware:	Any
OS:	Any

Description Lomash Gupta 2021-02-18 14:13:49 UTC

I would have expected to see an ESRCH if the provided gateway does not match the destination specified. See log below.

root@lgbsd:~/Desktop # netstat -r
Routing tables

Internet:
Destination        Gateway            Flags     Netif Expire
default            192.168.180.2      UGS         em0
localhost          link#2             UH          lo0
192.168.180.0/24   link#1             U           em0
192.168.180.128    link#1             UHS         lo0

Internet6:
Destination        Gateway            Flags     Netif Expire
::/96              localhost          UGRS        lo0
localhost          link#2             UH          lo0
::ffff:0.0.0.0/96  localhost          UGRS        lo0
fe80::/10          localhost          UGRS        lo0
fe80::%lo0/64      link#2             U           lo0
fe80::1%lo0        link#2             UHS         lo0
ff02::/16          localhost          UGRS        lo0

root@lgbsd:~/Desktop # route delete -net default 10.11.12.13
delete net default: gateway 10.11.12.13

root@lgbsd:~/Desktop # netstat -r
Routing tables

Internet:
Destination        Gateway            Flags     Netif Expire
localhost          link#2             UH          lo0
192.168.180.0/24   link#1             U           em0
192.168.180.128    link#1             UHS         lo0

Internet6:
Destination        Gateway            Flags     Netif Expire
::/96              localhost          UGRS        lo0
localhost          link#2             UH          lo0
::ffff:0.0.0.0/96  localhost          UGRS        lo0
fe80::/10          localhost          UGRS        lo0
fe80::%lo0/64      link#2             U           lo0
fe80::1%lo0        link#2             UHS         lo0
ff02::/16          localhost          UGRS        lo0


I can then also delete the destination subnet route and that causes all traffic to fail.

root@lgbsd:~/Desktop # route delete -net 192.168.180.0/24 10.11.12.13
delete net 192.168.180.0: gateway 10.11.12.13

root@lgbsd:~/Desktop # ping 192.168.180.1
PING 192.168.180.1 (192.168.180.1): 56 data bytes
ping: sendto: No route to host

Comment 1 Alexander V. Chernikov freebsd_committer

2021-02-18 22:31:29 UTC

IIRC gateway value is simply ignored in GENERIC kernel - the only thing that code checks is the prefix.

This part has been changed in 13 - if a gateway is specified, then the route gateway(s) are checked for the match.

I agree that 12 behaviour may look weird, however, that's what existed historically. 

I'm not sure if we can change it in FreeBSD 12, as we need to preserve compatibility any people may rely on this behaviour.


Re interface route: could you please clarify what do you think should be the expected behaviour?

Comment 2 Alexander V. Chernikov freebsd_committer

2022-05-30 12:17:10 UTC

I'll close this PR on Jun 5 if there are no other questions.