Messages in this thread | | | From | Jonathan Maxwell <> | Date | Wed, 21 Dec 2022 08:48:11 +1100 | Subject | Re: [net-next] ipv6: fix routing cache overflow for raw sockets |
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On Tue, Dec 20, 2022 at 11:35 PM Paolo Abeni <pabeni@redhat.com> wrote: > > On Mon, 2022-12-19 at 10:48 +1100, Jon Maxwell wrote: > > Sending Ipv6 packets in a loop via a raw socket triggers an issue where a > > route is cloned by ip6_rt_cache_alloc() for each packet sent. This quickly > > consumes the Ipv6 max_size threshold which defaults to 4096 resulting in > > these warnings: > > > > [1] 99.187805] dst_alloc: 7728 callbacks suppressed > > [2] Route cache is full: consider increasing sysctl net.ipv6.route.max_size. > > . > > . > > [300] Route cache is full: consider increasing sysctl net.ipv6.route.max_size. > > If I read correctly, the maximum number of dst that the raw socket can > use this way is limited by the number of packets it allows via the > sndbuf limit, right? >
Yes, but in my test sndbuf limit is never hit so it clones a route for every packet.
e.g:
output from C program sending 5000000 packets via a raw socket.
ip raw: total num pkts 5000000
# bpftrace -e 'kprobe:dst_alloc {@count[comm] = count()}' Attaching 1 probe...
@count[a.out]: 5000009
> Are other FLOWI_FLAG_KNOWN_NH users affected, too? e.g. nf_dup_ipv6, > ipvs, seg6? >
Any call to ip6_pol_route(s) where no res.nh->fib_nh_gw_family is 0 can do it. But we have only seen this for raw sockets so far.
Regards
Jon
> @DavidA: why do we need to create RTF_CACHE clones for KNOWN_NH flows? > > Thanks, > > Paolo >
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