netdev - Re: [PATCHv5 iproute2] ip route: ignore ENOENT during save if RT_TABLE

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Date:   Sun, 11 Jul 2021 14:12:43 +0300
From:   Alexander Mihalicyn <alexander@...alicyn.com>
To:     Roi Dayan <roid@...dia.com>
Cc:     patchwork-bot+netdevbpf@...nel.org, netdev@...r.kernel.org,
        dsahern@...il.com, stephen@...workplumber.org
Subject: Re: [PATCHv5 iproute2] ip route: ignore ENOENT during save if
 RT_TABLE_MAIN is being dumped

Thanks, Roi.

I will send a patch soon.

On Sun, Jul 11, 2021 at 2:09 PM Roi Dayan <roid@...dia.com> wrote:
>
>
>
> On 2021-07-11 1:59 PM, Roi Dayan wrote:
> >
> >
> > On 2021-07-07 5:50 PM, patchwork-bot+netdevbpf@...nel.org wrote:
> >> Hello:
> >>
> >> This patch was applied to iproute2/iproute2.git (refs/heads/main):
> >>
> >> On Wed,  7 Jul 2021 15:22:01 +0300 you wrote:
> >>> We started to use in-kernel filtering feature which allows to get only
> >>> needed tables (see iproute_dump_filter()). From the kernel side it's
> >>> implemented in net/ipv4/fib_frontend.c (inet_dump_fib),
> >>> net/ipv6/ip6_fib.c
> >>> (inet6_dump_fib). The problem here is that behaviour of "ip route save"
> >>> was changed after
> >>> c7e6371bc ("ip route: Add protocol, table id and device to dump
> >>> request").
> >>> If filters are used, then kernel returns ENOENT error if requested table
> >>> is absent, but in newly created net namespace even RT_TABLE_MAIN table
> >>> doesn't exist. It is really allocated, for instance, after issuing
> >>> "ip l set lo up".
> >>>
> >>> [...]
> >>
> >> Here is the summary with links:
> >>    - [PATCHv5,iproute2] ip route: ignore ENOENT during save if
> >> RT_TABLE_MAIN is being dumped
> >>
> >> https://git.kernel.org/pub/scm/network/iproute2/iproute2.git/commit/?id=459ce6e3d792
> >>
> >>
> >> You are awesome, thank you!
> >> --
> >> Deet-doot-dot, I am a bot.
> >> https://korg.docs.kernel.org/patchwork/pwbot.html
> >>
> >>
> >
> >
> > Hi,
> >
> > I didn't get a chance to check but after this commit the utility ss
> > is crashing from libnetlink.c
> >
> > (gdb) bt
> > #0  0x0000000000000000 in ?? ()
> > #1  0x0000000000418980 in rtnl_dump_done (a=0x7fffffffdc00, h=0x449c80)
> > at libnetlink.c:734
> > #2  rtnl_dump_filter_l (rth=rth@...ry=0x7fffffffdcf0,
> > arg=arg@...ry=0x7fffffffdc00) at libnetlink.c:893
> > #3  0x00000000004197a2 in rtnl_dump_filter_nc
> > (rth=rth@...ry=0x7fffffffdcf0, filter=filter@...ry=0x40cdf0
> > <show_one_inet_sock>,
> >      arg1=arg1@...ry=0x7fffffffdca0, nc_flags=nc_flags@...ry=0) at
> > libnetlink.c:957
> > #4  0x0000000000406dc7 in inet_show_netlink (dump_fp=dump_fp@...ry=0x0,
> > protocol=protocol@...ry=255, f=0x42e900 <current_filter>) at ss.c:3638
> > #5  0x0000000000404db3 in raw_show (f=0x42e900 <current_filter>) at
> > ss.c:3939
> >
> >
> > if I revert this commit I can run the ss utility ok.
> >
> > Thanks,
> > Roi
>
> I found for me ss crashed using a->errhndlr but it could be null
> in rtnl_dump_done()
>
> I see a second usage of a->errhndlr in rtnl_dump_error()
>
>