From: 曹煜 <cao88yu@gmail.com>
To: Nico Schottelius <nico.schottelius@ungleich.ch>
Cc: "Daniel Gröber" <dxld@darkboxed.org>,
"Roman Mamedov" <rm@romanrm.net>, tlhackque <tlhackque@yahoo.com>,
wireguard@lists.zx2c4.com
Subject: Re: Src addr code review (Was: Source IP incorrect on multi homed systems)
Date: Mon, 20 Feb 2023 19:21:07 +0800 [thread overview]
Message-ID: <CACu-5+1sJV9wLN_unK_C4GK32sOjmqaB0MK1vbw__GaNFLZgPQ@mail.gmail.com> (raw)
In-Reply-To: <87sff0oc06.fsf@ungleich.ch>
Hi Nico,
That issue was closed by myself, but the patch didn't get applied
cause the issue was came from wireguard itself, and the maintener told
me that I should send my patch to wireguard upstream (but I just gave
up for sending it to wireguard team).
Nico Schottelius <nico.schottelius@ungleich.ch> 于2023年2月20日周一 18:41写道:
>
>
> Hello 曹煜,
>
> on github it seems your patch was applied / the issue was closed - is
> that the correct current status?
>
> Best regards,
>
> Nico
>
> 曹煜 <cao88yu@gmail.com> writes:
>
> > Hi all,
> > I've hacked that source code myself months ago, and it works well on
> > my use case (I have 4 dual stack pppoe wan set on my openwrt router,
> > and seted a wireguard sever on it), my hack will pickup the dst_addr
> > from incoming handshake packet in kernel sk_buff, and then use that
> > addr as src_addr to reply.
> > I'm not good at source code, and I know that my hack may be ugly, but
> > it works, hope this patch can help:
> > https://github.com/openwrt/packages/issues/9538#issuecomment-1150592803
> >
> > Daniel Gröber <dxld@darkboxed.org> 于2023年2月20日周一 06:42写道:
> >>
> >> Hi,
> >>
> >> I though it might be useful to do some quick and dirty code review instead
> >> of speculating wildly to figure out where these source IP selection
> >> problems could be coming from ;)
> >>
> >> From previous code deep dives I know the udp_tunnel_xmit_skb function is
> >> where tunnel packets get handed off to the kernel. So in
> >> net/wireguard/socket.c:send4 we have:
> >>
> >> udp_tunnel_xmit_skb(rt, sock, skb, fl.saddr, fl.daddr, ds,
> >> ip4_dst_hoplimit(&rt->dst), 0, fl.fl4_sport,
> >> fl.fl4_dport, false, false);
> >>
> >> Where fl.saddr is the source address that's supposedly wrong (sometimes? I
> >> guess?) Where does that come from?
> >>
> >> Let's look at the code (heavily culled):
> >>
> >> struct flowi4 fl = {
> >> .saddr = endpoint->src4.s_addr,
> >> };
> >> if (cache)
> >> rt = dst_cache_get_ip4(cache, &fl.saddr);
> >> if (!rt) {
> >> if (unlikely(!inet_confirm_addr(sock_net(sock), NULL, 0,
> >> fl.saddr, RT_SCOPE_HOST)))
> >> fl.saddr = 0;
> >> if (unlikely(endpoint->src_if4 && ((IS_ERR(rt) &&
> >> PTR_ERR(rt) == -EINVAL) || (!IS_ERR(rt) &&
> >> rt->dst.dev->ifindex != endpoint->src_if4))))
> >> fl.saddr = 0;
> >>
> >> Well it's initialized from endpoint->src4.s_addr, overwritten with zero in
> >> some cases, which I believe lets the kernel do it's regular source addr
> >> selection, and populated from something called dst_cache at some callsites.
> >>
> >> @Nico could it perhaps simply be that you're hitting one of these zero'ing
> >> cases and that's why it's using regular kernel src addr selection instead
> >> of the cached endpoint src4 address?
> >>
> >> The first case !inet_confirm_addr(..., RT_SCOPE_HOST) ought to confirm that
> >> the saddr is actually still a local address. Makes sens if the address we
> >> remembered was removed from the interface we can't use it anymore.
> >>
> >> The second case looks like it's checking if the (sometimes cached) src_if4
> >> interface index is still what the route we're about to use points to.
> >>
> >> If neither of those seem likely we can keep reading :)
> >>
> >> --Daniel
> >>
> >>
> >>
>
>
> --
> Sustainable and modern Infrastructures by ungleich.ch
next prev parent reply other threads:[~2023-02-20 11:21 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-18 20:14 Source IP incorrect on multi homed systems Nico Schottelius
[not found] ` <CAHx9msc1cNV80YU7HRmQ9gsjSEiVZ=pb31aYqfP62hy8DeuGZA@mail.gmail.com>
2023-02-18 22:34 ` Nico Schottelius
2023-02-19 0:45 ` Mike O'Connor
2023-02-19 8:01 ` Nico Schottelius
2023-02-19 9:19 ` Mikma
2023-02-19 12:04 ` Nico Schottelius
2023-02-19 12:10 ` Nico Schottelius
2023-02-19 18:59 ` Peter Linder
[not found] ` <2ed829aaed9fec59ac2a9b32c4ce0a9005b8d8b850be81c81a226791855fe4eb@mu.id>
2023-02-19 12:13 ` Nico Schottelius
2023-02-19 14:39 ` Christoph Loesch
2023-02-19 16:32 ` David Kerr
2023-02-19 16:54 ` Sebastian Hyrvall
2023-02-19 18:04 ` Janne Johansson
2023-02-19 18:08 ` Sebastian Hyrvall
2023-02-19 20:11 ` Nico Schottelius
2023-02-19 17:05 ` tlhackque
2023-02-19 18:37 ` David Kerr
2023-02-19 18:52 ` tlhackque
2023-02-19 18:42 ` tlhackque
2023-02-19 20:18 ` Nico Schottelius
2023-02-19 20:42 ` Roman Mamedov
2023-02-19 21:19 ` Nico Schottelius
2023-02-19 22:06 ` tlhackque
2023-02-19 22:42 ` Src addr code review (Was: Source IP incorrect on multi homed systems) Daniel Gröber
2023-02-20 0:28 ` 曹煜
2023-02-20 10:40 ` Nico Schottelius
2023-02-20 11:21 ` 曹煜 [this message]
2023-02-20 9:47 ` Nico Schottelius
2023-02-20 20:43 ` dxld
2023-02-19 21:39 ` Source IP incorrect on multi homed systems tlhackque
[not found] ` <CADGd2DoE6TCtCxxWL7JWyNW5+yy_Pe+9MNzHznbudMWLTXQreA@mail.gmail.com>
2023-02-19 18:30 ` Fwd: " John Lauro
2023-02-19 22:28 ` tlhackque
2023-02-20 0:58 ` Luiz Angelo Daros de Luca
2023-02-19 20:02 ` Nico Schottelius
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