[Qemu-devel] [PATCH v2 08/11] net: Untangle nested qemu_send_packet

[Jan Kiszka <jan.kiszka@siemens.com>]

Queue packets that are send during an ongoing packet delivery. This
ensures that packets will always arrive in their logical order at each
client of a VLAN. Currently, slirp generates such immediate relies, and
e.g. packet-sniffing clients on the same VLAN may get confused.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---

 net.c |   36 ++++++++++++++++++++++++++++++------
 net.h |   11 +++++++++++
 2 files changed, 41 insertions(+), 6 deletions(-)

diff --git a/net.c b/net.c
index 1ee7504..5156cc1 100644
--- a/net.c
+++ b/net.c
@@ -402,22 +402,46 @@ int qemu_can_send_packet(VLANClientState *vc1)
     return 0;
 }
 
-void qemu_send_packet(VLANClientState *vc1, const uint8_t *buf, int size)
+static void
+qemu_deliver_packet(VLANClientState *sender, const uint8_t *buf, int size)
 {
-    VLANState *vlan = vc1->vlan;
     VLANClientState *vc;
 
-    if (vc1->link_down)
+    for (vc = sender->vlan->first_client; vc != NULL; vc = vc->next) {
+        if (vc != sender && !vc->link_down) {
+            vc->fd_read(vc->opaque, buf, size);
+        }
+    }
+}
+
+void qemu_send_packet(VLANClientState *vc, const uint8_t *buf, int size)
+{
+    VLANState *vlan = vc->vlan;
+    VLANPacket *packet;
+
+    if (vc->link_down)
         return;
 
 #ifdef DEBUG_NET
     printf("vlan %d send:\n", vlan->id);
     hex_dump(stdout, buf, size);
 #endif
-    for(vc = vlan->first_client; vc != NULL; vc = vc->next) {
-        if (vc != vc1 && !vc->link_down) {
-            vc->fd_read(vc->opaque, buf, size);
+    if (vlan->delivering) {
+        packet = qemu_malloc(sizeof(VLANPacket) + size);
+        packet->next = vlan->send_queue;
+        packet->sender = vc;
+        packet->size = size;
+        memcpy(packet->data, buf, size);
+        vlan->send_queue = packet;
+    } else {
+        vlan->delivering = 1;
+        qemu_deliver_packet(vc, buf, size);
+        while ((packet = vlan->send_queue) != NULL) {
+            qemu_deliver_packet(packet->sender, packet->data, packet->size);
+            vlan->send_queue = packet->next;
+            qemu_free(packet);
         }
+        vlan->delivering = 0;
     }
 }
 
diff --git a/net.h b/net.h
index 413f705..fe5ece7 100644
--- a/net.h
+++ b/net.h
@@ -29,11 +29,22 @@ struct VLANClientState {
     char info_str[256];
 };
 
+typedef struct VLANPacket VLANPacket;
+
+struct VLANPacket {
+    struct VLANPacket *next;
+    VLANClientState *sender;
+    int size;
+    uint8_t data[0];
+};
+
 struct VLANState {
     int id;
     VLANClientState *first_client;
     struct VLANState *next;
     unsigned int nb_guest_devs, nb_host_devs;
+    VLANPacket *send_queue;
+    int delivering;
 };
 
 VLANState *qemu_find_vlan(int id);