[Qemu-devel] [RFC PATCH 3/3] filter-rewriter: rewrite tcp packet to keep secondary connection

[Zhang Chen]

We will rewrite tcp packet secondary received and sent.

Signed-off-by: Zhang Chen <address@hidden>
Signed-off-by: Li Zhijian <address@hidden>
Signed-off-by: Wen Congyang <address@hidden>
---
 net/filter-rewriter.c | 94 +++++++++++++++++++++++++++++++++++++++++++++++++--
 trace-events          |  3 ++
 2 files changed, 95 insertions(+), 2 deletions(-)

diff --git a/net/filter-rewriter.c b/net/filter-rewriter.c
index 12f88c5..86a2f53 100644
--- a/net/filter-rewriter.c
+++ b/net/filter-rewriter.c
@@ -21,6 +21,7 @@
 #include "qemu/main-loop.h"
 #include "qemu/iov.h"
 #include "net/checksum.h"
+#include "trace.h"
 
 #define FILTER_COLO_REWRITER(obj) \
     OBJECT_CHECK(RewriterState, (obj), TYPE_FILTER_REWRITER)
@@ -64,6 +65,75 @@ static int is_tcp_packet(Packet *pkt)
     }
 }
 
+static int handle_primary_tcp_pkt(NetFilterState *nf,
+                                  Connection *conn,
+                                  Packet *pkt)
+{
+    struct tcphdr *tcp_pkt;
+
+    tcp_pkt = (struct tcphdr *)pkt->transport_layer;
+
+    if (trace_event_get_state(TRACE_COLO_FILTER_REWRITER_DEBUG)) {
+        char *sdebug, *ddebug;
+        sdebug = strdup(inet_ntoa(pkt->ip->ip_src));
+        ddebug = strdup(inet_ntoa(pkt->ip->ip_dst));
+        fprintf(stderr, "%s: src/dst: %s/%s p: seq/ack=%u/%u"
+                "  flags=%x\n", __func__, sdebug, ddebug,
+                ntohl(tcp_pkt->th_seq), ntohl(tcp_pkt->th_ack),
+                tcp_pkt->th_flags);
+        g_free(sdebug);
+        g_free(ddebug);
+    }
+
+    if (((tcp_pkt->th_flags & (TH_ACK | TH_SYN)) == TH_ACK)) {
+        /* save primary colo tcp packet seq */
+        conn->primary_seq = ntohl(tcp_pkt->th_ack) - 1;
+
+        /* adjust tcp seq to make secondary guest handle it */
+        tcp_pkt->th_ack = htonl(conn->secondary_seq + 1);
+        net_checksum_calculate((uint8_t *)pkt->data, pkt->size);
+    }
+
+    return 0;
+}
+
+static int handle_secondary_tcp_pkt(NetFilterState *nf,
+                                    Connection *conn,
+                                    Packet *pkt)
+{
+    struct tcphdr *tcp_pkt;
+
+    tcp_pkt = (struct tcphdr *)pkt->transport_layer;
+
+    if (trace_event_get_state(TRACE_COLO_FILTER_REWRITER_DEBUG)) {
+        char *sdebug, *ddebug;
+        sdebug = strdup(inet_ntoa(pkt->ip->ip_src));
+        ddebug = strdup(inet_ntoa(pkt->ip->ip_dst));
+        printf("handle_secondary_tcp_pkt conn->secondary_seq = %u,\n",
+               conn->secondary_seq);
+        printf("handle_secondary_tcp_pkt conn->primary_seq = %u,\n",
+               conn->primary_seq);
+        fprintf(stderr, "%s: src/dst: %s/%s p: seq/ack=%u/%u"
+                "  flags=%x\n", __func__, sdebug, ddebug,
+                ntohl(tcp_pkt->th_seq), ntohl(tcp_pkt->th_ack),
+                tcp_pkt->th_flags);
+        g_free(sdebug);
+        g_free(ddebug);
+    }
+
+    if (((tcp_pkt->th_flags & (TH_ACK | TH_SYN)) == (TH_ACK | TH_SYN))) {
+        /* save client's seq */
+        conn->secondary_seq = ntohl(tcp_pkt->th_seq);
+    }
+
+    if ((tcp_pkt->th_flags & (TH_ACK | TH_SYN)) == TH_ACK) {
+        tcp_pkt->th_seq = htonl(conn->primary_seq + 1);
+        net_checksum_calculate((uint8_t *)pkt->data, pkt->size);
+    }
+
+    return 0;
+}
+
 static ssize_t colo_rewriter_receive_iov(NetFilterState *nf,
                                          NetClientState *sender,
                                          unsigned flags,
@@ -106,10 +176,30 @@ static ssize_t colo_rewriter_receive_iov(NetFilterState 
*nf,
         if (sender == nf->netdev) {
             /* This packet is sent by netdev itself */
             /* NET_FILTER_DIRECTION_TX */
-            /* handle_primary_tcp_pkt */
+            if (!handle_primary_tcp_pkt(nf, conn, pkt)) {
+                qemu_net_queue_send(s->incoming_queue, sender, 0,
+                (const uint8_t *)pkt->data, pkt->size, NULL);
+                packet_destroy(pkt, NULL);
+                pkt = NULL;
+                /*
+                 * We block the packet here,after rewrite pkt
+                 * and will send it
+                 */
+                return 1;
+            }
         } else {
             /* NET_FILTER_DIRECTION_RX */
-            /* handle_secondary_tcp_pkt */
+            if (!handle_secondary_tcp_pkt(nf, conn, pkt)) {
+                qemu_net_queue_send(s->incoming_queue, sender, 0,
+                (const uint8_t *)pkt->data, pkt->size, NULL);
+                packet_destroy(pkt, NULL);
+                pkt = NULL;
+                /*
+                 * We block the packet here,after rewrite pkt
+                 * and will send it
+                 */
+                return 1;
+            }
         }
     }
 
diff --git a/trace-events b/trace-events
index 6686cdf..5d798c6 100644
--- a/trace-events
+++ b/trace-events
@@ -1927,3 +1927,6 @@ colo_compare_icmp_miscompare_mtu(const char *sta, int 
size) ": %s  %d"
 colo_compare_ip_info(int psize, const char *sta, const char *stb, int ssize, 
const char *stc, const char *std) "ppkt size = %d, ip_src = %s, ip_dst = %s, 
spkt size = %d, ip_src = %s, ip_dst = %s"
 colo_old_packet_check_found(int64_t old_time) "%" PRId64
 colo_compare_miscompare(void) ""
+
+# net/filter-rewriter.c
+colo_filter_rewriter_debug(void) ""
-- 
2.7.4