Another roaming problem

[Toke Høiland-Jørgensen]

Toke Høiland-Jørgensen <toke at toke.dk> writes:

> Toke Høiland-Jørgensen <toke at toke.dk> writes:
>
>> "Jason A. Donenfeld" <Jason at zx2c4.com> writes:
>>
>>> On Thu, Mar 8, 2018 at 6:50 PM, Toke Høiland-Jørgensen <toke at toke.dk> wrote:
>>>> Well, I do generally setup routing in a somewhat unusual manner.
>>>>
>>>> I can try to capture some packet dumps tomorrow to poke into it a bit more. Anything in particular I should look for?
>>>
>>> One thing to examine is when WireGuard calls
>>> `socket_clear_peer_endpoint_src'. This makes wireguard forget the
>>> source address that it should be using and fall back to the default.
>>> You could add a pr_info(...) call in this function. I have an inkling
>>> that I make calls to this function too zealously and in potentially
>>> unneeded places, such as on handshake transmission retries.
>>>
>>> I'm headed out of town super soon, so likely debugging this will have
>>> to wait until I'm back, but do let me know what you find, and we'll
>>> get this fixed up upon return.
>>
>> Well, completely failed to reproduce it; everything works as its
>> supposed to now (wireguard correctly picks the public IP as its source
>> address when replying to the client).
>>
>> Not sure if I have changed something in my setup or what is going on;
>> but at least I can roam now, so I'm happy ;)
>
> Scratch that, it's still happening; just not straight away upon roaming.
> It is definitely a timeout thing; installed a kprobe on the function you
> mentioned and got this strack trace when it switches IP:
>
> TIME(s)            FUNCTION
> 104.999884129      socket_clear_peer_endpoint_src
> 	socket_clear_peer_endpoint_src
> 	expired_new_handshake
> 	call_timer_fn
> 	run_timer_softirq
> 	__do_softirq
> 	irq_exit
> 	smp_apic_timer_interrupt
> 	__irqentry_text_start
> 	cpuidle_enter_state
> 	do_idle
> 	cpu_startup_entry
> 	start_secondary
> 	secondary_startup_64

And leaving it running a bit more, there is also a call from
expired_retransmit_handshake:

449.079751015      socket_clear_peer_endpoint_src
	socket_clear_peer_endpoint_src
	expired_retransmit_handshake
	call_timer_fn
	run_timer_softirq
	__do_softirq
	irq_exit
	smp_apic_timer_interrupt
	__irqentry_text_start
	cpuidle_enter_state
	do_idle
	cpu_startup_entry
	start_secondary
	secondary_startup_64


-Toke