tcp: fix handling of TCP RST segments missing timestamps

[tuexen]

Summary

A TCP RST segment should be processed even it is missing TCP timestamps.

[dmgk]

With this patch applied, the Go test suite passes on both current (818390ce0ca) and stable/12 (49038d1723a). Thanks!

[kevans]

I'm afraid that I can't provide much better input than dmgk already has, but this does conform to my interpretation of RFC7323 from a brief read at the referenced section.

[rscheff]

Functionally, I concur that this is the right way to handle RST packets.

From an implementation, perhaps having the check for TH_RST and the V_tcp_tolerate_missing_ts sysctl of D28142 in a combined || check, rather than two fully independent branches (which is likely if D28142 and D28143 are applied independently).

[tuexen]

In D28143#629142, @rscheff wrote:

Functionally, I concur that this is the right way to handle RST packets.

From an implementation, perhaps having the check for TH_RST and the V_tcp_tolerate_missing_ts sysctl of D28142 in a combined || check, rather than two fully independent branches (which is likely if D28142 and D28143 are applied independently).

I will apply this patch first, then update the D28142 using an ||. I want to keep them separate, since this is a fix of a bug, D28142 is adding a sysctl.

[rscheff]

Sounds like a good plan!

[tuexen]

Committed in cc3c34859eab1b317d0f38731355b53f7d978c97.