Re: [PATCH v13 07/10] vhost-user: add vhost-user

[David Gibson <david@gibson.dropbear.id.au>]

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On Wed, Nov 20, 2024 at 01:40:50PM +0100, Laurent Vivier wrote:
> On 20/11/2024 04:33, David Gibson wrote:
> > > +	vu_set_vnethdr(vdev, flags_elem[0].in_sg[0].iov_base, 1);
> > > +
> > > +	eh = vu_eth(flags_elem[0].in_sg[0].iov_base);
> > > +
> > > +	memcpy(eh->h_dest, c->guest_mac, sizeof(eh->h_dest));
> > > +	memcpy(eh->h_source, c->our_tap_mac, sizeof(eh->h_source));
> > > +
> > > +	if (CONN_V4(conn)) {
> > > +		struct tcp_payload_t *payload;
> > > +		struct iphdr *iph;
> > > +		uint32_t seq;
> > > +
> > > +		eh->h_proto = htons(ETH_P_IP);
> > > +
> > > +		iph = vu_ip(flags_elem[0].in_sg[0].iov_base);
> > > +		*iph = (struct iphdr)L2_BUF_IP4_INIT(IPPROTO_TCP);
> > > +
> > > +		payload = vu_payloadv4(flags_elem[0].in_sg[0].iov_base);
> > > +		memset(&payload->th, 0, sizeof(payload->th));
> > > +		payload->th.doff = offsetof(struct tcp_payload_t, data) / 4;
> > > +		payload->th.ack = 1;
> > > +
> > > +		seq = conn->seq_to_tap;
> > > +		ret = tcp_prepare_flags(c, conn, flags, &payload->th,
> > > +					(struct tcp_syn_opts *)payload->data,
> > > +					&optlen);
> > > +		if (ret <= 0) {
> > > +			vu_queue_rewind(vq, 1);
> > > +			return ret;
> > > +		}
> > > +
> > > +		l4len = tcp_fill_headers4(conn, NULL, iph, payload, optlen,
> > > +					  NULL, seq, true);
> > > +		l2len = sizeof(*iph);
> > Much of the above duplicates tcp_vu_prepare().  Any chance you could
> > call into it instead?
> 
> I tried but tcp_fill_headersX() needs the length computed in
> tcp_prepare_flags() but tcp_prepare_flags() needs to be after
> tcp_vu_prepare() because tcp_vu_prepare() resets the TCP header and
> tcp_prepare_flags() updates it with the flags.
> tcp_prepare_flags() should be called in the middle of tcp_vu_prepare().
> It's really simpler to duplicate the code of tcp_vu_prepare() in
> tcp_vu_send_flag() rather than to call tcp_vu_prepare() from
> tcp_vu_send_flag().

Ah, yes, I see your point.

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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