On Thu, Aug 23, 2012 at 4:26 AM, Asias He <asias.hejun@xxxxxxxxx> wrote:
> Respect guest tcp window size and stop sending tcp segments to guest
> if guest's receive window is closed.
>
> This fixes the TCP hang I'm seeing where guest and host are transferring
> big chuck of data.
Awesome!
> This problem was not triggered when guest and external host
> communicates, probably because guest to external host communication
> walks through real network and is much slower than guest and host
> communication. Thus, guest's receive window has little chance to be
> closed.
>
> Signed-off-by: Asias He <asias.hejun@xxxxxxxxx>
> ---
> tools/kvm/include/kvm/uip.h | 1 +
> tools/kvm/net/uip/tcp.c | 28 ++++++++++++++++++++++------
> 2 files changed, 23 insertions(+), 6 deletions(-)
>
> diff --git a/tools/kvm/include/kvm/uip.h b/tools/kvm/include/kvm/uip.h
> index 4497f6a..191029b 100644
> --- a/tools/kvm/include/kvm/uip.h
> +++ b/tools/kvm/include/kvm/uip.h
> @@ -235,6 +235,7 @@ struct uip_tcp_socket {
> pthread_t thread;
> u32 dport, sport;
> u32 guest_acked;
> + u16 window_size;
> /*
> * Initial Sequence Number
> */
> diff --git a/tools/kvm/net/uip/tcp.c b/tools/kvm/net/uip/tcp.c
> index 586a45c..cf46bac 100644
> --- a/tools/kvm/net/uip/tcp.c
> +++ b/tools/kvm/net/uip/tcp.c
> @@ -167,25 +167,38 @@ static int uip_tcp_payload_send(struct uip_tcp_socket *sk, u8 flag, u16 payload_
> static void *uip_tcp_socket_thread(void *p)
> {
> struct uip_tcp_socket *sk;
> - u8 *payload;
> - int ret;
> + u8 *payload, *pos;
> + int len, left, ret;
>
> sk = p;
>
> payload = malloc(UIP_MAX_TCP_PAYLOAD);
> - sk->payload = payload;
> - if (!sk->payload)
> + if (!payload)
> goto out;
>
> while (1) {
> + pos = payload;
>
> ret = read(sk->fd, payload, UIP_MAX_TCP_PAYLOAD);
>
> if (ret <= 0 || ret > UIP_MAX_TCP_PAYLOAD)
> goto out;
>
> - uip_tcp_payload_send(sk, UIP_TCP_FLAG_ACK, ret);
> + left = ret;
> +
> + while (left > 0) {
> + while ((len = sk->guest_acked + sk->window_size - sk->seq_server) <= 0)
> + usleep(100);
So what exactly is this piece of code trying to accomplish? Surely
there's some more reasonable way to handle it?
> + sk->payload = pos;
> + if (len > left)
> + len = left;
> + if (len > UIP_MAX_TCP_PAYLOAD)
> + len = UIP_MAX_TCP_PAYLOAD;
> + left -= len;
>
> + pos += len;
> + uip_tcp_payload_send(sk, UIP_TCP_FLAG_ACK, len);
> + }
> }
>
> out:
> @@ -199,7 +212,7 @@ out:
>
> sk->read_done = 1;
>
> - free(sk->payload);
> + free(payload);
> pthread_exit(NULL);
>
> return NULL;
> @@ -250,6 +263,8 @@ int uip_tx_do_ipv4_tcp(struct uip_tx_arg *arg)
> if (!sk)
> return -1;
>
> + sk->window_size = ntohs(tcp->win);
> +
> /*
> * Setup ISN number
> */
> @@ -276,6 +291,7 @@ int uip_tx_do_ipv4_tcp(struct uip_tx_arg *arg)
> if (!sk)
> return -1;
>
> + sk->window_size = ntohs(tcp->win);
> sk->guest_acked = ntohl(tcp->ack);
>
> if (uip_tcp_is_fin(tcp)) {
> --
> 1.7.11.4
>
> --
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