Messages in this thread Patch in this message | | | Date | Sat, 2 Dec 2023 17:16:12 +0000 | From | Simon Horman <> | Subject | Re: [PATCH v4 6/7] net/tcp: Store SNEs + SEQs on ao_info |
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On Wed, Nov 29, 2023 at 04:57:20PM +0000, Dmitry Safonov wrote: > RFC 5925 (6.2): > > TCP-AO emulates a 64-bit sequence number space by inferring when to > > increment the high-order 32-bit portion (the SNE) based on > > transitions in the low-order portion (the TCP sequence number). > > snd_sne and rcv_sne are the upper 4 bytes of extended SEQ number. > Unfortunately, reading two 4-bytes pointers can't be performed > atomically (without synchronization). > > In order to avoid locks on TCP fastpath, let's just double-account for > SEQ changes: snd_una/rcv_nxt will be lower 4 bytes of snd_sne/rcv_sne. > > Fixes: 64382c71a557 ("net/tcp: Add TCP-AO SNE support") > Signed-off-by: Dmitry Safonov <dima@arista.com>
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> diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h > index 647781080613..b8ef25d4b632 100644 > --- a/include/net/tcp_ao.h > +++ b/include/net/tcp_ao.h > @@ -121,8 +121,8 @@ struct tcp_ao_info { > * - for time-wait sockets the basis is tw_rcv_nxt/tw_snd_nxt. > * tw_snd_nxt is not expected to change, while tw_rcv_nxt may. > */ > - u32 snd_sne; > - u32 rcv_sne; > + u64 snd_sne; > + u64 rcv_sne; > refcount_t refcnt; /* Protects twsk destruction */ > struct rcu_head rcu; > };
Hi Dmitry,
In tcp_ao.c:tcp_ao_connect_init() there is a local variable:
struct tcp_ao_info *ao_info;
And the following assignment occurs:
ao_info->snd_sne = htonl(tp->write_seq);
Is this still correct in light of the change of the type of snd_sne? Flagged by Sparse.
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