Messages in this thread | | | Date | Tue, 20 Dec 2022 08:10:32 -0700 | Subject | Re: [net-next] ipv6: fix routing cache overflow for raw sockets | From | David Ahern <> |
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On 12/20/22 5:35 AM, Paolo Abeni 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? > > Are other FLOWI_FLAG_KNOWN_NH users affected, too? e.g. nf_dup_ipv6, > ipvs, seg6? > > @DavidA: why do we need to create RTF_CACHE clones for KNOWN_NH flows? > > Thanks, > > Paolo >
If I recall the details correctly: that sysctl limit was added back when ipv6 routes were managed as dst_entries and there was a desire to allow an admin to limit the memory consumed. At this point in time, IPv6 is more inline with IPv4 - a separate struct for fib entries from dst entries. That "Route cache is full" message is now out of date since this is dst_entries which have a gc mechanism.
IPv4 does not limit the number of dst_entries that can be allocated (ip_rt_max_size is the sysctl variable behind the ipv4 version of max_size and it is a no-op). IPv6 can probably do the same here?
I do not believe the suggested flag is the right change.
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