Re: [Qemu-devel] [PATCH V3] net: always walk through filters in reverse if traffic is egress

[Jason Wang]

On 01/26/2016 01:00 PM, Li Zhijian wrote:
> Previously, if we attach more than filters for one netdev, IN/OUT traffic pass
> through filters in a same order.
> ingress: netdev ->filter1 ->filter2 ->...filter[n] ->emulated device
> egress: emulated device ->filter1 ->filter2 ->...filter[n] ->netdev.
>
> But some scenes, we hope filters handle the egress traffic in a reverse order.
> For example, in colo-proxy (will be implemented later), we have a redirector
> filter and a colo-rewriter filter, we need the filter behavior like that:
> ingress(->)/egress(<-): chardev<->redirector<->colo-rewriter<->emulated device
>
> After this changes, egress traffic always pass through filters in a reverse
> order.
>
> Signed-off-by: Wen Congyang <address@hidden>
> Signed-off-by: Li Zhijian <address@hidden>
> Reviewed-by: Yang Hongyang <address@hidden>

Applied with minor tweaks on commit log:

https://github.com/jasowang/qemu/commit/ec96442e398191f84aab824180aa83cd5eda0010

and use:

QTAILQ_HEAD(NetFilterHead, NetFilterState) filters;

instead.

Thanks

> ---
>  include/net/net.h |  4 +++-
>  net/filter.c      | 21 +++++++++++++++++++--
>  net/net.c         | 20 +++++++++++++++-----
>  3 files changed, 37 insertions(+), 8 deletions(-)
>
> diff --git a/include/net/net.h b/include/net/net.h
> index 7af3e15..1d807cc 100644
> --- a/include/net/net.h
> +++ b/include/net/net.h
> @@ -79,6 +79,8 @@ typedef struct NetClientInfo {
>      SetVnetBE *set_vnet_be;
>  } NetClientInfo;
>  
> +QTAILQ_HEAD(NetFilterHead, NetFilterState);
> +
>  struct NetClientState {
>      NetClientInfo *info;
>      int link_down;
> @@ -92,7 +94,7 @@ struct NetClientState {
>      NetClientDestructor *destructor;
>      unsigned int queue_index;
>      unsigned rxfilter_notify_enabled:1;
> -    QTAILQ_HEAD(, NetFilterState) filters;
> +    struct NetFilterHead filters;
>  };
>  
>  typedef struct NICState {
> diff --git a/net/filter.c b/net/filter.c
> index 5d90f83..17a8398 100644
> --- a/net/filter.c
> +++ b/net/filter.c
> @@ -34,6 +34,22 @@ ssize_t qemu_netfilter_receive(NetFilterState *nf,
>      return 0;
>  }
>  
> +static NetFilterState *netfilter_next(NetFilterState *nf,
> +                                      NetFilterDirection dir)
> +{
> +    NetFilterState *next;
> +
> +    if (dir == NET_FILTER_DIRECTION_TX) {
> +        /* forward walk through filters */
> +        next = QTAILQ_NEXT(nf, next);
> +    } else {
> +        /* reverse order */
> +        next = QTAILQ_PREV(nf, NetFilterHead, next);
> +    }
> +
> +    return next;
> +}
> +
>  ssize_t qemu_netfilter_pass_to_next(NetClientState *sender,
>                                      unsigned flags,
>                                      const struct iovec *iov,
> @@ -43,7 +59,7 @@ ssize_t qemu_netfilter_pass_to_next(NetClientState *sender,
>      int ret = 0;
>      int direction;
>      NetFilterState *nf = opaque;
> -    NetFilterState *next = QTAILQ_NEXT(nf, next);
> +    NetFilterState *next = NULL;
>  
>      if (!sender || !sender->peer) {
>          /* no receiver, or sender been deleted, no need to pass it further */
> @@ -61,6 +77,7 @@ ssize_t qemu_netfilter_pass_to_next(NetClientState *sender,
>          direction = nf->direction;
>      }
>  
> +    next = netfilter_next(nf, direction);
>      while (next) {
>          /*
>           * if qemu_netfilter_pass_to_next been called, means that
> @@ -73,7 +90,7 @@ ssize_t qemu_netfilter_pass_to_next(NetClientState *sender,
>          if (ret) {
>              return ret;
>          }
> -        next = QTAILQ_NEXT(next, next);
> +        next = netfilter_next(next, direction);
>      }
>  
>      /*
> diff --git a/net/net.c b/net/net.c
> index 87dd356..c929c41 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -580,11 +580,21 @@ static ssize_t filter_receive_iov(NetClientState *nc,
>      ssize_t ret = 0;
>      NetFilterState *nf = NULL;
>  
> -    QTAILQ_FOREACH(nf, &nc->filters, next) {
> -        ret = qemu_netfilter_receive(nf, direction, sender, flags, iov,
> -                                     iovcnt, sent_cb);
> -        if (ret) {
> -            return ret;
> +    if (direction == NET_FILTER_DIRECTION_TX) {
> +        QTAILQ_FOREACH(nf, &nc->filters, next) {
> +            ret = qemu_netfilter_receive(nf, direction, sender, flags, iov,
> +                                         iovcnt, sent_cb);
> +            if (ret) {
> +                return ret;
> +            }
> +        }
> +    } else {
> +        QTAILQ_FOREACH_REVERSE(nf, &nc->filters, NetFilterHead, next) {
> +            ret = qemu_netfilter_receive(nf, direction, sender, flags, iov,
> +                                         iovcnt, sent_cb);
> +            if (ret) {
> +                return ret;
> +            }
>          }
>      }
>