Re: [Qemu-devel] [PATCH v2 5/9] netfilter: hook packets before net queue send

[Jason Wang <jasowang@redhat.com>]

On 07/31/2015 12:13 PM, Yang Hongyang wrote:
> Capture packets that will be sent.
>
> Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
> ---
>  include/net/filter.h |  8 +++++++
>  net/filter.c         |  1 +
>  net/net.c            | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++-
>  3 files changed, 75 insertions(+), 1 deletion(-)
>
> diff --git a/include/net/filter.h b/include/net/filter.h
> index 1b6f896..93579c1 100644
> --- a/include/net/filter.h
> +++ b/include/net/filter.h
> @@ -19,11 +19,19 @@ enum {
>  };
>  
>  typedef void (FilterCleanup) (NetFilterState *);
> +/*
> + * Return:
> + *   0: finished handling the packet, we should continue
> + *   size: filter stolen this packet, we stop pass this packet further
> + */
> +typedef ssize_t (FilterReceiveIOV)(NetFilterState *, NetClientState *sender,
> +                                   unsigned flags, const struct iovec *, int);
>  
>  typedef struct NetFilterInfo {
>      NetFilterOptionsKind type;
>      size_t size;
>      FilterCleanup *cleanup;
> +    FilterReceiveIOV *receive_iov;

Please move this to patch 2.

>  } NetFilterInfo;
>  
>  struct NetFilterState {
> diff --git a/net/filter.c b/net/filter.c
> index b3a2285..1ae9344 100644
> --- a/net/filter.c
> +++ b/net/filter.c
> @@ -29,6 +29,7 @@ NetFilterState *qemu_new_net_filter(NetFilterInfo *info,
>      NetFilterState *nf;
>  
>      assert(info->size >= sizeof(NetFilterState));
> +    assert(info->receive_iov);
>  
>      nf = g_malloc0(info->size);
>      nf->info = info;
> diff --git a/net/net.c b/net/net.c
> index 22748e0..b55d934 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -24,6 +24,7 @@
>  #include "config-host.h"
>  
>  #include "net/net.h"
> +#include "net/filter.h"
>  #include "clients.h"
>  #include "hub.h"
>  #include "net/slirp.h"
> @@ -592,6 +593,42 @@ int qemu_can_send_packet(NetClientState *sender)
>      return 1;
>  }
>  
> +static ssize_t filter_receive_iov(NetClientState *nc, int chain,
> +                                  NetClientState *sender,
> +                                  unsigned flags,
> +                                  const struct iovec *iov,
> +                                  int iovcnt) {
> +    ssize_t ret = 0;
> +    Filter *filter = NULL;
> +    NetFilterState *nf = NULL;
> +    ssize_t size = iov_size(iov, iovcnt);
> +
> +    QTAILQ_FOREACH(filter, &nc->filters, next) {
> +        nf = filter->nf;
> +        if (nf->chain == chain || nf->chain == NET_FILTER_ALL) {
> +            ret = nf->info->receive_iov(nf, sender, flags, iov, iovcnt);
> +            if (ret == size) {
> +                return ret;
> +            }
> +        }
> +    }

So if a packet is being stolen or blocked by one filter, it could only
be flushed to destination? I think we need an API to flush it into next
filter.

> +
> +    return ret;
> +}
> +
> +static ssize_t filter_receive(NetClientState *nc, int chain,
> +                              NetClientState *sender,
> +                              unsigned flags,
> +                              const uint8_t *data,
> +                              size_t size) {
> +    struct iovec iov = {
> +        .iov_base = (void *)data,
> +        .iov_len = size
> +    };
> +
> +    return filter_receive_iov(nc, chain, sender, flags, &iov, 1);
> +}
> +
>  ssize_t qemu_deliver_packet(NetClientState *sender,
>                              unsigned flags,
>                              const uint8_t *data,
> @@ -663,6 +700,7 @@ static ssize_t qemu_send_packet_async_with_flags(NetClientState *sender,
>                                                   NetPacketSent *sent_cb)
>  {
>      NetQueue *queue;
> +    int ret;
>  
>  #ifdef DEBUG_NET
>      printf("qemu_send_packet_async:\n");
> @@ -673,6 +711,18 @@ static ssize_t qemu_send_packet_async_with_flags(NetClientState *sender,
>          return size;
>      }
>  
> +    /* Let filters handle the packet first */
> +    ret = filter_receive(sender, NET_FILTER_OUT, sender, flags, buf, size);
> +    if (ret == size) {
> +        return size;
> +    }
> +
> +    ret = filter_receive(sender->peer, NET_FILTER_IN,
> +                         sender, flags, buf, size);
> +    if (ret == size) {
> +        return size;
> +    }
> +
>      queue = sender->peer->incoming_queue;
>  
>      return qemu_net_queue_send(queue, sender, flags, buf, size, sent_cb);
> @@ -743,9 +793,24 @@ ssize_t qemu_sendv_packet_async(NetClientState *sender,
>                                  NetPacketSent *sent_cb)
>  {
>      NetQueue *queue;
> +    int size = iov_size(iov, iovcnt);
> +    int ret;
>  
>      if (sender->link_down || !sender->peer) {
> -        return iov_size(iov, iovcnt);
> +        return size;
> +    }
> +
> +    /* Let filters handle the packet first */
> +    ret = filter_receive_iov(sender, NET_FILTER_OUT,
> +                             sender, QEMU_NET_PACKET_FLAG_NONE, iov, iovcnt);
> +    if (ret == size) {
> +        return size;
> +    }
> +
> +    ret = filter_receive_iov(sender->peer, NET_FILTER_IN,
> +                             sender, QEMU_NET_PACKET_FLAG_NONE, iov, iovcnt);
> +    if (ret == size) {
> +        return size;
>      }
>  
>      queue = sender->peer->incoming_queue;