| Message ID | cover.1650575919.git.peilin.ye@bytedance.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | ip_gre, ip6_gre: o_seqno fixes | expand |
Hello: This series was applied to netdev/net.git (master) by David S. Miller <davem@davemloft.net>: On Thu, 21 Apr 2022 15:06:39 -0700 you wrote: > From: Peilin Ye <peilin.ye@bytedance.com> > > Hi all, > > As pointed out [1] by Jakub Kicinski, currently using TUNNEL_SEQ in > collect_md mode is racy for [IP6]GRE[TAP] devices, since they (typically, > e.g. if created using "ip") use lockless TX. > > [...] Here is the summary with links: - [net,1/3] ip_gre: Make o_seqno start from 0 in native mode https://git.kernel.org/netdev/net/c/ff827beb706e - [net,2/3] ip6_gre: Make o_seqno start from 0 in native mode https://git.kernel.org/netdev/net/c/fde98ae91f79 - [net,3/3] ip_gre, ip6_gre: Fix race condition on o_seqno in collect_md mode https://git.kernel.org/netdev/net/c/31c417c948d7 You are awesome, thank you!
From: Peilin Ye <peilin.ye@bytedance.com> Hi all, As pointed out [1] by Jakub Kicinski, currently using TUNNEL_SEQ in collect_md mode is racy for [IP6]GRE[TAP] devices, since they (typically, e.g. if created using "ip") use lockless TX. Patch [3/3] fixes it by making o_seqno atomic_t. As mentioned by Eric Dumazet in commit b790e01aee74 ("ip_gre: lockless xmit"), making o_seqno atomic_t increases "chance for packets being out of order at receiver" when using lockless TX. Another way to fix it would be: users must specify "external" and "oseq" at the same time if they want the kernel to allow using TUNNEL_SEQ (e.g. via eBPF) in collect_md mode, but that would break userspace. I found another issue while reading the code: patches [1,2/3] make o_seqno start from 0 in native mode, as described in RFC 2890 [2] section 2.2.: "The first datagram is sent with a sequence number of 0." Now we could make [IP6]GRE[TAP] (and probably [IP6]ERSPAN ?) devices completely NETIF_F_LLTX, but that's out of scope of this fix and will be sent as separate [net-next] patches. [1] https://lore.kernel.org/netdev/20220415191133.0597a79a@kernel.org/ [2] https://datatracker.ietf.org/doc/html/rfc2890#section-2.2 Thanks, Peilin Ye (3): ip_gre: Make o_seqno start from 0 in native mode ip6_gre: Make o_seqno start from 0 in native mode ip_gre, ip6_gre: Fix race condition on o_seqno in collect_md mode include/net/ip6_tunnel.h | 2 +- include/net/ip_tunnels.h | 2 +- net/ipv4/ip_gre.c | 12 +++++------- net/ipv6/ip6_gre.c | 16 ++++++++-------- 4 files changed, 15 insertions(+), 17 deletions(-)