netdev - Re: [PATCH net-next 4/4] net/tls: byte swap device req TCP seq no upon setting

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Message-ID: <20190425123802.5d1ab5a4@cakuba.netronome.com>
Date:   Thu, 25 Apr 2019 12:38:02 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Saeed Mahameed <saeedm@...lanox.com>
Cc:     "davem@...emloft.net" <davem@...emloft.net>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "davejwatson@...com" <davejwatson@...com>,
        "oss-drivers@...ronome.com" <oss-drivers@...ronome.com>,
        Boris Pismenny <borisp@...lanox.com>,
        "john.fastabend@...il.com" <john.fastabend@...il.com>,
        Aviad Yehezkel <aviadye@...lanox.com>,
        "alexei.starovoitov@...il.com" <alexei.starovoitov@...il.com>,
        "simon.horman@...ronome.com" <simon.horman@...ronome.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 4/4] net/tls: byte swap device req TCP seq no
 upon setting

On Thu, 25 Apr 2019 19:31:51 +0000, Saeed Mahameed wrote:
> > diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
> > index cb368efe3567..6686013b4e9e 100644
> > --- a/net/tls/tls_device.c
> > +++ b/net/tls/tls_device.c
> > @@ -567,7 +567,7 @@ void (struct sock *sk, u32
> > seq, u64 rcd_sn)
> >  
> >  	rx_ctx = tls_offload_ctx_rx(tls_ctx);
> >  	resync_req = atomic64_read(&rx_ctx->resync_req);
> > -	req_seq = ntohl(resync_req >> 32) - ((u32)TLS_HEADER_SIZE - 1);
> > +	req_seq = (resync_req >> 32) - ((u32)TLS_HEADER_SIZE - 1);  
> 
> this is not equivalent to what was before, 
> resync_req is expected to be in network order, 
> (TLS_HEADER_SIZE -1) is still in cpu indianness.

Naw, I think they are both in host order.

The driver passes network order.

But the stack has it in host order, this is the call site:

#ifdef CONFIG_TLS_DEVICE
	handle_device_resync(strp->sk, TCP_SKB_CB(skb)->seq + rxm->offset,
			     *(u64*)tls_ctx->rx.rec_seq);
#endif

The value passed by the driver used to be byte swapped when read from
the atomic, but I moved the byte swap to when it's stored to the atomic.
We used to have a weird situation where the atomic would have a be32 on
the top 32bits, and lower 32 bits would store the 1, in host order.

IOW the tls_offload_rx_resync_request() is the only thing setting this
value and I moved the byte swap there.

$ git grep '.->resync_req'
include/net/tls.h:      atomic64_set(&rx_ctx->resync_req, ((u64)ntohl(seq) << 32) | 1);
net/tls/tls_device.c:   resync_req = atomic64_read(&rx_ctx->resync_req);
net/tls/tls_device.c:       atomic64_try_cmpxchg(&rx_ctx->resync_req, &resync_req, 0))

Did I miss something or screw up tls_offload_rx_resync_request()?