stream/tcp: support TCP fast open

src/stream-tcp-private.h

@@ -186,6 +186,8 @@ enum
 #define STREAMTCP_FLAG_APP_LAYER_DISABLED           0x2000
 /** Stream can be bypass */
 #define STREAMTCP_FLAG_BYPASS                       0x4000
+/** SSN uses TCP Fast Open */
+#define STREAMTCP_FLAG_TCP_FAST_OPEN                0x8000
 
 /*
  * Per STREAM flags

src/stream-tcp.c

@@ -1058,6 +1058,16 @@ static int StreamTcpPacketStateNone(ThreadVars *tv, Packet *p,
             SCLogDebug("ssn %p: SACK permited on SYN packet", ssn);
         }
 
+        if (TCP_HAS_TFO(p)) {
+            ssn->flags |= STREAMTCP_FLAG_TCP_FAST_OPEN;
+            if (p->payload_len) {
+                StreamTcpUpdateNextSeq(ssn, &ssn->client, (ssn->client.next_seq + p->payload_len));
+                SCLogNotice("ssn: %p (TFO) [len: %d] isn %u base_seq %u next_seq %u payload len %u",
+                        ssn, p->tcpvars.tfo.len, ssn->client.isn, ssn->client.base_seq, ssn->client.next_seq, p->payload_len);
+                StreamTcpReassembleHandleSegment(tv, stt->ra_ctx, ssn, &ssn->client, p, pq);
+            }
+        }
+
         SCLogDebug("ssn %p: ssn->client.isn %" PRIu32 ", "
                 "ssn->client.next_seq %" PRIu32 ", ssn->client.last_ack "
                 "%"PRIu32"", ssn, ssn->client.isn, ssn->client.next_seq,
@@ -1504,16 +1514,31 @@ static int StreamTcpPacketStateSynSent(ThreadVars *tv, Packet *p,
             return -1;
         }
 
-        /* Check if the SYN/ACK packet ack's the earlier
-         * received SYN packet. */
-        if (!(SEQ_EQ(TCP_GET_ACK(p), ssn->client.isn + 1))) {
-            StreamTcpSetEvent(p, STREAM_3WHS_SYNACK_WITH_WRONG_ACK);
-            SCLogDebug("ssn %p: ACK mismatch, packet ACK %" PRIu32 " != "
+        if (!(TCP_HAS_TFO(p) || (ssn->flags & STREAMTCP_FLAG_TCP_FAST_OPEN))) {
+            /* Check if the SYN/ACK packet ack's the earlier
+             * received SYN packet. */
+            if (!(SEQ_EQ(TCP_GET_ACK(p), ssn->client.isn + 1))) {
+                StreamTcpSetEvent(p, STREAM_3WHS_SYNACK_WITH_WRONG_ACK);
+                SCLogDebug("ssn %p: ACK mismatch, packet ACK %" PRIu32 " != "
+                        "%" PRIu32 " from stream", ssn, TCP_GET_ACK(p),
+                        ssn->client.isn + 1);
+                return -1;
+            }
+        } else {
+            if (!(SEQ_EQ(TCP_GET_ACK(p), ssn->client.next_seq))) {
+                StreamTcpSetEvent(p, STREAM_3WHS_SYNACK_WITH_WRONG_ACK);
+                SCLogDebug("ssn %p: (TFO) ACK mismatch, packet ACK %" PRIu32 " != "
+                        "%" PRIu32 " from stream", ssn, TCP_GET_ACK(p),
+                        ssn->client.next_seq);
+                return -1;
+            }
+            SCLogDebug("ssn %p: (TFO) ACK match, packet ACK %" PRIu32 " == "
                     "%" PRIu32 " from stream", ssn, TCP_GET_ACK(p),
-                    ssn->client.isn + 1);
-            return -1;
-        }
+                    ssn->client.next_seq);
 
+            ssn->flags |= STREAMTCP_FLAG_TCP_FAST_OPEN;
+            StreamTcpPacketSetState(p, ssn, TCP_ESTABLISHED);
+        }
         StreamTcp3whsSynAckUpdate(ssn, p, /* no queue override */NULL);
 
     } else if (p->tcph->th_flags & TH_SYN) {
@@ -1857,6 +1882,9 @@ static int StreamTcpPacketStateSynRecv(ThreadVars *tv, Packet *p,
                 SCLogDebug("ssn %p: ACK received on midstream SYN/ACK "
                         "pickup session",ssn);
                 /* fall through */
+            } else if (ssn->flags & STREAMTCP_FLAG_TCP_FAST_OPEN) {
+                SCLogDebug("ssn %p: ACK received on TFO session",ssn);
+                /* fall through */
 
             } else {
                 /* if we missed traffic between the S/SA and the current
@@ -2019,11 +2047,16 @@ static int StreamTcpPacketStateSynRecv(ThreadVars *tv, Packet *p,
                     &ssn->client, p, pq);
 
         /* toclient packet: after having missed the 3whs's final ACK */
-        } else if (ack_indicates_missed_3whs_ack_packet &&
+        } else if ((ack_indicates_missed_3whs_ack_packet ||
+                    (ssn->flags & STREAMTCP_FLAG_TCP_FAST_OPEN)) &&
                 SEQ_EQ(TCP_GET_ACK(p), ssn->client.last_ack) &&
                 SEQ_EQ(TCP_GET_SEQ(p), ssn->server.next_seq))
         {
-            SCLogDebug("ssn %p: packet fits perfectly after a missed 3whs-ACK", ssn);
+            if (ack_indicates_missed_3whs_ack_packet) {
+                SCLogDebug("ssn %p: packet fits perfectly after a missed 3whs-ACK", ssn);
+            } else {
+                SCLogDebug("ssn %p: (TFO) expected packet fits perfectly after SYN/ACK", ssn);
+            }
 
             StreamTcpUpdateNextSeq(ssn, &ssn->server, (TCP_GET_SEQ(p) + p->payload_len));