Bill Auerbach wrote:
> Thanks Jonathan,
>
> I see that it outputs a segment in tcp_output, but I'm not calling
> tcp_output. I'm calling tcp_write multiple times. I do see it append a
> segment in tcp_enqueue. Shouldn't tcp_output pass a linked pbuf chain with
> enough data up to the MSS? If I call tcp_write 10 times with 10 "Hello
> World"s, I would think one Ethernet frame would be sent with a call to
> ip_output with one pbuf pointer with 11 payloads (the header and 10 data
> payloads).
Yes that's what should happen. The bit of magic that does this is nearish
the bottom of tcp_enqueue in tcp_out.c:
/* If there is room in the last pbuf on the unsent queue,
chain the first pbuf on the queue together with that. */
if (useg != NULL &&
TCP_TCPLEN(useg) != 0 &&
!(TCPH_FLAGS(useg->tcphdr) & (TCP_SYN | TCP_FIN)) &&
!(flags & (TCP_SYN | TCP_FIN)) &&
/* fit within max seg size */
useg->len + queue->len <= pcb->mss) {
/* Remove TCP header from first segment of our to-be-queued list */
if(pbuf_header(queue->p, -TCP_HLEN)) {
/* Can we cope with this failing? Just assert for now */
LWIP_ASSERT("pbuf_header failed\n", 0);
TCP_STATS_INC(tcp.err);
goto memerr;
}
pbuf_cat(useg->p, queue->p);
useg->len += queue->len;
useg->next = queue->next;
[snip]
I can only assume that your subsequent tcp_writes are not matching the 'if'
condition. Maybe you could debug it (or add a little print statement) to
find out why. It is possible there may be a bug around.
Jifl
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