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

[Li Zhijian]

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>
---
 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;
+            }
         }
     }
 
-- 
2.5.0