[Qemu-devel] [RFC Patch 07/10] TCP control packet handling.

[wexu@redhat.com]

From: Wei Xu <wexu@redhat.com>

All the 'SYN' packets will be bypassed, and flag with 'FIN/RST' set
will signal all the cached packets in the same connection to be purged,
this is to avoid out of data on the line.

Signed-off-by: Wei Xu <wexu@redhat.com>
---
 hw/net/virtio-net.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 1ca3dd5..042b538 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -41,6 +41,12 @@
 
 #define VIRTIO_HEADER   12    /* Virtio net header size */
 #define IP_OFFSET (VIRTIO_HEADER + sizeof(struct eth_header))
+
+#define IP4_ADDR_OFFSET (IP_OFFSET + 12)    /* ipv4 address start */
+#define TCP4_OFFSET (IP_OFFSET + sizeof(struct ip_header)) /* tcp4 header */
+#define TCP4_PORT_OFFSET TCP4_OFFSET        /* tcp4 port offset */
+#define IP4_ADDR_SIZE   8                   /* ipv4 saddr + daddr */
+#define TCP_PORT_SIZE   4                   /* sport + dport */
 #define TCP_WINDOW      65535
 
 /* ip4 max payload, 16 bits in the header */
@@ -1850,6 +1856,27 @@ static int32_t virtio_net_rsc_try_coalesce4(NetRscChain *chain,
                                     o_data, &o_ip->ip_len, MAX_IP4_PAYLOAD);
 }
 
+
+/* Pakcets with 'SYN' should bypass, other flag should be sent after drain
+ * to prevent out of order */
+static int virtio_net_rsc_parse_tcp_ctrl(uint8_t *ip, uint16_t offset)
+{
+    uint16_t tcp_flag;
+    struct tcp_header *tcp;
+
+    tcp = (struct tcp_header *)(ip + offset);
+    tcp_flag = htons(tcp->th_offset_flags) & 0x3F;
+    if (tcp_flag & TH_SYN) {
+        return RSC_BYPASS;
+    }
+
+    if (tcp_flag & (TH_FIN | TH_URG | TH_RST)) {
+        return RSC_FINAL;
+    }
+
+    return 0;
+}
+
 static size_t virtio_net_rsc_callback(NetRscChain *chain, NetClientState *nc,
                 const uint8_t *buf, size_t size, VirtioNetCoalesce *coalesce)
 {
@@ -1895,12 +1922,51 @@ static size_t virtio_net_rsc_callback(NetRscChain *chain, NetClientState *nc,
     return virtio_net_rsc_cache_buf(chain, nc, buf, size);
 }
 
+/* Drain a connection data, this is to avoid out of order segments */
+static size_t virtio_net_rsc_drain_one(NetRscChain *chain, NetClientState *nc,
+                    const uint8_t *buf, size_t size, uint16_t ip_start,
+                    uint16_t ip_size, uint16_t tcp_port, uint16_t port_size)
+{
+    NetRscSeg *seg, *nseg;
+
+    QTAILQ_FOREACH_SAFE(seg, &chain->buffers, next, nseg) {
+        if (memcmp(buf + ip_start, seg->buf + ip_start, ip_size)
+            || memcmp(buf + tcp_port, seg->buf + tcp_port, port_size)) {
+            continue;
+        }
+        if ((chain->proto == ETH_P_IP) && seg->is_coalesced) {
+            virtio_net_rsc_ipv4_checksum(seg);
+        }
+
+        virtio_net_do_receive(seg->nc, seg->buf, seg->size);
+
+        QTAILQ_REMOVE(&chain->buffers, seg, next);
+        g_free(seg->buf);
+        g_free(seg);
+        break;
+    }
+
+    return virtio_net_do_receive(nc, buf, size);
+}
 static size_t virtio_net_rsc_receive4(void *opq, NetClientState* nc,
                                       const uint8_t *buf, size_t size)
 {
+    int32_t ret;
+    struct ip_header *ip;
     NetRscChain *chain;
 
     chain = (NetRscChain *)opq;
+    ip = (struct ip_header *)(buf + IP_OFFSET);
+
+    ret = virtio_net_rsc_parse_tcp_ctrl((uint8_t *)ip,
+                                        (0xF & ip->ip_ver_len) << 2);
+    if (RSC_BYPASS == ret) {
+        return virtio_net_do_receive(nc, buf, size);
+    } else if (RSC_FINAL == ret) {
+        return virtio_net_rsc_drain_one(chain, nc, buf, size, IP4_ADDR_OFFSET,
+                                IP4_ADDR_SIZE, TCP4_PORT_OFFSET, TCP_PORT_SIZE);
+    }
+
     return virtio_net_rsc_callback(chain, nc, buf, size,
                                    virtio_net_rsc_try_coalesce4);
 }
-- 
2.4.0