stream: still inspect packets dropped by stream

The detect engine would bypass packets that are set as dropped. This
seems sane, as these packets are going to be dropped anyway.

However, it lead to the following corner case: stream events that
triggered the drop could not be matched on the rules. The packet
with the event wouldn't make it to the detect engine due to the bypass.

This patch changes the logic to not bypass DROP packets anymore.
Packets that are dropped by the stream engine will set the no payload
inspection flag, so avoid needless cost.
static int StreamTcpPacketStateNone(ThreadVars *tv, Packet *p,
                        StreamTcpThread *stt, TcpSession *ssn, PacketQueue *pq)
{
    if (p->tcph->th_flags & TH_RST) {
        StreamTcpSetEvent(p, STREAM_RST_BUT_NO_SESSION);
        SCLogDebug("RST packet received, no session setup");
        return -1;

    } else if (p->tcph->th_flags & TH_FIN) {
        StreamTcpSetEvent(p, STREAM_FIN_BUT_NO_SESSION);
        SCLogDebug("FIN packet received, no session setup");
        return -1;

    /* SYN/ACK */
    } else if ((p->tcph->th_flags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) {
        if (stream_config.midstream == FALSE &&
                stream_config.async_oneside == FALSE)
            return 0;

        if (ssn == NULL) {
            ssn = StreamTcpNewSession(p, stt->ssn_pool_id);
            if (ssn == NULL) {
                StatsIncr(tv, stt->counter_tcp_ssn_memcap);
                return -1;
            }
            StatsIncr(tv, stt->counter_tcp_sessions);
        }
        /* set the state */
        StreamTcpPacketSetState(p, ssn, TCP_SYN_RECV);
        SCLogDebug("ssn %p: =~ midstream picked ssn state is now "
                "TCP_SYN_RECV", ssn);
        ssn->flags |= STREAMTCP_FLAG_MIDSTREAM;
        /* Flag used to change the direct in the later stage in the session */
        ssn->flags |= STREAMTCP_FLAG_MIDSTREAM_SYNACK;
        if (stream_config.async_oneside) {
            SCLogDebug("ssn %p: =~ ASYNC", ssn);
            ssn->flags |= STREAMTCP_FLAG_ASYNC;
        }

        /* sequence number & window */
        ssn->server.isn = TCP_GET_SEQ(p);
        STREAMTCP_SET_RA_BASE_SEQ(&ssn->server, ssn->server.isn);
        ssn->server.next_seq = ssn->server.isn + 1;
        ssn->server.window = TCP_GET_WINDOW(p);
        SCLogDebug("ssn %p: server window %u", ssn, ssn->server.window);

        ssn->client.isn = TCP_GET_ACK(p) - 1;
        STREAMTCP_SET_RA_BASE_SEQ(&ssn->client, ssn->client.isn);
        ssn->client.next_seq = ssn->client.isn + 1;

        ssn->client.last_ack = TCP_GET_ACK(p);
        ssn->server.last_ack = TCP_GET_SEQ(p);

        ssn->server.next_win = ssn->server.last_ack + ssn->server.window;

        /** If the client has a wscale option the server had it too,
         *  so set the wscale for the server to max. Otherwise none
         *  will have the wscale opt just like it should. */
        if (TCP_HAS_WSCALE(p)) {
            ssn->client.wscale = TCP_GET_WSCALE(p);
            ssn->server.wscale = TCP_WSCALE_MAX;
            SCLogDebug("ssn %p: wscale enabled. client %u server %u",
                    ssn, ssn->client.wscale, ssn->server.wscale);
        }

        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,
                ssn->client.last_ack);
        SCLogDebug("ssn %p: ssn->server.isn %"PRIu32", ssn->server.next_seq"
                " %"PRIu32", ssn->server.last_ack %"PRIu32"", ssn,
                ssn->server.isn, ssn->server.next_seq,
                ssn->server.last_ack);

        /* Set the timestamp value for both streams, if packet has timestamp
         * option enabled.*/
        if (TCP_HAS_TS(p)) {
            ssn->server.last_ts = TCP_GET_TSVAL(p);
            ssn->client.last_ts = TCP_GET_TSECR(p);
            SCLogDebug("ssn %p: ssn->server.last_ts %" PRIu32" "
                    "ssn->client.last_ts %" PRIu32"", ssn,
                    ssn->server.last_ts, ssn->client.last_ts);

            ssn->flags |= STREAMTCP_FLAG_TIMESTAMP;

            ssn->server.last_pkt_ts = p->ts.tv_sec;
            if (ssn->server.last_ts == 0)
                ssn->server.flags |= STREAMTCP_STREAM_FLAG_ZERO_TIMESTAMP;
            if (ssn->client.last_ts == 0)
                ssn->client.flags |= STREAMTCP_STREAM_FLAG_ZERO_TIMESTAMP;

        } else {
            ssn->server.last_ts = 0;
            ssn->client.last_ts = 0;
        }

        if (TCP_GET_SACKOK(p) == 1) {
            ssn->flags |= STREAMTCP_FLAG_SACKOK;
            SCLogDebug("ssn %p: SYN/ACK with SACK permitted, assuming "
                    "SACK permitted for both sides", ssn);
        }

        /* packet thinks it is in the wrong direction, flip it */
        StreamTcpPacketSwitchDir(ssn, p);

    } else if (p->tcph->th_flags & TH_SYN) {
        if (ssn == NULL) {
            ssn = StreamTcpNewSession(p, stt->ssn_pool_id);
            if (ssn == NULL) {
                StatsIncr(tv, stt->counter_tcp_ssn_memcap);
                return -1;
            }

            StatsIncr(tv, stt->counter_tcp_sessions);
        }

        /* set the state */
        StreamTcpPacketSetState(p, ssn, TCP_SYN_SENT);
        SCLogDebug("ssn %p: =~ ssn state is now TCP_SYN_SENT", ssn);

        if (stream_config.async_oneside) {
            SCLogDebug("ssn %p: =~ ASYNC", ssn);
            ssn->flags |= STREAMTCP_FLAG_ASYNC;
        }

        /* set the sequence numbers and window */
        ssn->client.isn = TCP_GET_SEQ(p);
        STREAMTCP_SET_RA_BASE_SEQ(&ssn->client, ssn->client.isn);
        ssn->client.next_seq = ssn->client.isn + 1;

        /* Set the stream timestamp value, if packet has timestamp option
         * enabled. */
        if (TCP_HAS_TS(p)) {
            ssn->client.last_ts = TCP_GET_TSVAL(p);
            SCLogDebug("ssn %p: %02x", ssn, ssn->client.last_ts);

            if (ssn->client.last_ts == 0)
                ssn->client.flags |= STREAMTCP_STREAM_FLAG_ZERO_TIMESTAMP;

            ssn->client.last_pkt_ts = p->ts.tv_sec;
            ssn->client.flags |= STREAMTCP_STREAM_FLAG_TIMESTAMP;
        }

        ssn->server.window = TCP_GET_WINDOW(p);
        if (TCP_HAS_WSCALE(p)) {
            ssn->flags |= STREAMTCP_FLAG_SERVER_WSCALE;
            ssn->server.wscale = TCP_GET_WSCALE(p);
        }

        if (TCP_GET_SACKOK(p) == 1) {
            ssn->flags |= STREAMTCP_FLAG_CLIENT_SACKOK;
            SCLogDebug("ssn %p: SACK permited on SYN packet", ssn);
        }

        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,
                ssn->client.last_ack);

    } else if (p->tcph->th_flags & TH_ACK) {
        if (stream_config.midstream == FALSE)
            return 0;

        if (ssn == NULL) {
            ssn = StreamTcpNewSession(p, stt->ssn_pool_id);
            if (ssn == NULL) {
                StatsIncr(tv, stt->counter_tcp_ssn_memcap);
                return -1;
            }
            StatsIncr(tv, stt->counter_tcp_sessions);
        }
        /* set the state */
        StreamTcpPacketSetState(p, ssn, TCP_ESTABLISHED);
        SCLogDebug("ssn %p: =~ midstream picked ssn state is now "
                "TCP_ESTABLISHED", ssn);

        ssn->flags = STREAMTCP_FLAG_MIDSTREAM;
        ssn->flags |= STREAMTCP_FLAG_MIDSTREAM_ESTABLISHED;
        if (stream_config.async_oneside) {
            SCLogDebug("ssn %p: =~ ASYNC", ssn);
            ssn->flags |= STREAMTCP_FLAG_ASYNC;
        }

        /** window scaling for midstream pickups, we can't do much other
         *  than assume that it's set to the max value: 14 */
        ssn->client.wscale = TCP_WSCALE_MAX;
        ssn->server.wscale = TCP_WSCALE_MAX;

        /* set the sequence numbers and window */
        ssn->client.isn = TCP_GET_SEQ(p) - 1;
        STREAMTCP_SET_RA_BASE_SEQ(&ssn->client, ssn->client.isn);
        ssn->client.next_seq = TCP_GET_SEQ(p) + p->payload_len;
        ssn->client.window = TCP_GET_WINDOW(p) << ssn->client.wscale;
        ssn->client.last_ack = TCP_GET_SEQ(p);
        ssn->client.next_win = ssn->client.last_ack + ssn->client.window;
        SCLogDebug("ssn %p: ssn->client.isn %u, ssn->client.next_seq %u",
                ssn, ssn->client.isn, ssn->client.next_seq);

        ssn->server.isn = TCP_GET_ACK(p) - 1;
        STREAMTCP_SET_RA_BASE_SEQ(&ssn->server, ssn->server.isn);
        ssn->server.next_seq = ssn->server.isn + 1;
        ssn->server.last_ack = TCP_GET_ACK(p);
        ssn->server.next_win = ssn->server.last_ack;

        SCLogDebug("ssn %p: ssn->client.next_win %"PRIu32", "
                "ssn->server.next_win %"PRIu32"", ssn,
                ssn->client.next_win, ssn->server.next_win);
        SCLogDebug("ssn %p: ssn->client.last_ack %"PRIu32", "
                "ssn->server.last_ack %"PRIu32"", ssn,
                ssn->client.last_ack, ssn->server.last_ack);

        /* Set the timestamp value for both streams, if packet has timestamp
         * option enabled.*/
        if (TCP_HAS_TS(p)) {
            ssn->client.last_ts = TCP_GET_TSVAL(p);
            ssn->server.last_ts = TCP_GET_TSECR(p);
            SCLogDebug("ssn %p: ssn->server.last_ts %" PRIu32" "
                    "ssn->client.last_ts %" PRIu32"", ssn,
                    ssn->server.last_ts, ssn->client.last_ts);

            ssn->flags |= STREAMTCP_FLAG_TIMESTAMP;

            ssn->client.last_pkt_ts = p->ts.tv_sec;
            if (ssn->server.last_ts == 0)
                ssn->server.flags |= STREAMTCP_STREAM_FLAG_ZERO_TIMESTAMP;
            if (ssn->client.last_ts == 0)
                ssn->client.flags |= STREAMTCP_STREAM_FLAG_ZERO_TIMESTAMP;

        } else {
            ssn->server.last_ts = 0;
            ssn->client.last_ts = 0;
        }

        StreamTcpReassembleHandleSegment(tv, stt->ra_ctx, ssn, &ssn->client, p, pq);

        ssn->flags |= STREAMTCP_FLAG_SACKOK;
        SCLogDebug("ssn %p: assuming SACK permitted for both sides", ssn);

    } else {
        SCLogDebug("default case");
    }

    return 0;
}

static int StreamTcpPacketStateNone(ThreadVars *tv, Packet *p,
                        StreamTcpThread *stt, TcpSession *ssn, PacketQueue *pq)
{
    if (p->tcph->th_flags & TH_RST) {
        StreamTcpSetEvent(p, STREAM_RST_BUT_NO_SESSION);
        SCLogDebug("RST packet received, no session setup");
        return -1;

    } else if (p->tcph->th_flags & TH_FIN) {
        StreamTcpSetEvent(p, STREAM_FIN_BUT_NO_SESSION);
        SCLogDebug("FIN packet received, no session setup");
        return -1;

    /* SYN/ACK */
    } else if ((p->tcph->th_flags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) {
        if (stream_config.midstream == FALSE &&
                stream_config.async_oneside == FALSE)
            return 0;

        if (ssn == NULL) {
            ssn = StreamTcpNewSession(p, stt->ssn_pool_id);
            if (ssn == NULL) {
                StatsIncr(tv, stt->counter_tcp_ssn_memcap);
                return -1;
            }
            StatsIncr(tv, stt->counter_tcp_sessions);
        }
        /* set the state */
        StreamTcpPacketSetState(p, ssn, TCP_SYN_RECV);
        SCLogDebug("ssn %p: =~ midstream picked ssn state is now "
                "TCP_SYN_RECV", ssn);
        ssn->flags |= STREAMTCP_FLAG_MIDSTREAM;
        /* Flag used to change the direct in the later stage in the session */
        ssn->flags |= STREAMTCP_FLAG_MIDSTREAM_SYNACK;
        if (stream_config.async_oneside) {
            SCLogDebug("ssn %p: =~ ASYNC", ssn);
            ssn->flags |= STREAMTCP_FLAG_ASYNC;
        }

        /* sequence number & window */
        ssn->server.isn = TCP_GET_SEQ(p);
        STREAMTCP_SET_RA_BASE_SEQ(&ssn->server, ssn->server.isn);
        ssn->server.next_seq = ssn->server.isn + 1;
        ssn->server.window = TCP_GET_WINDOW(p);
        SCLogDebug("ssn %p: server window %u", ssn, ssn->server.window);

        ssn->client.isn = TCP_GET_ACK(p) - 1;
        STREAMTCP_SET_RA_BASE_SEQ(&ssn->client, ssn->client.isn);
        ssn->client.next_seq = ssn->client.isn + 1;

        ssn->client.last_ack = TCP_GET_ACK(p);
        ssn->server.last_ack = TCP_GET_SEQ(p);

        ssn->server.next_win = ssn->server.last_ack + ssn->server.window;

        /** If the client has a wscale option the server had it too,
         *  so set the wscale for the server to max. Otherwise none
         *  will have the wscale opt just like it should. */
        if (TCP_HAS_WSCALE(p)) {
            ssn->client.wscale = TCP_GET_WSCALE(p);
            ssn->server.wscale = TCP_WSCALE_MAX;
            SCLogDebug("ssn %p: wscale enabled. client %u server %u",
                    ssn, ssn->client.wscale, ssn->server.wscale);
        }

        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,
                ssn->client.last_ack);
        SCLogDebug("ssn %p: ssn->server.isn %"PRIu32", ssn->server.next_seq"
                " %"PRIu32", ssn->server.last_ack %"PRIu32"", ssn,
                ssn->server.isn, ssn->server.next_seq,
                ssn->server.last_ack);

        /* Set the timestamp value for both streams, if packet has timestamp
         * option enabled.*/
        if (TCP_HAS_TS(p)) {
            ssn->server.last_ts = TCP_GET_TSVAL(p);
            ssn->client.last_ts = TCP_GET_TSECR(p);
            SCLogDebug("ssn %p: ssn->server.last_ts %" PRIu32" "
                    "ssn->client.last_ts %" PRIu32"", ssn,
                    ssn->server.last_ts, ssn->client.last_ts);

            ssn->flags |= STREAMTCP_FLAG_TIMESTAMP;

            ssn->server.last_pkt_ts = p->ts.tv_sec;
            if (ssn->server.last_ts == 0)
                ssn->server.flags |= STREAMTCP_STREAM_FLAG_ZERO_TIMESTAMP;
            if (ssn->client.last_ts == 0)
                ssn->client.flags |= STREAMTCP_STREAM_FLAG_ZERO_TIMESTAMP;

        } else {
            ssn->server.last_ts = 0;
            ssn->client.last_ts = 0;
        }

        if (TCP_GET_SACKOK(p) == 1) {
            ssn->flags |= STREAMTCP_FLAG_SACKOK;
            SCLogDebug("ssn %p: SYN/ACK with SACK permitted, assuming "
                    "SACK permitted for both sides", ssn);
        }

        /* packet thinks it is in the wrong direction, flip it */
        StreamTcpPacketSwitchDir(ssn, p);

    } else if (p->tcph->th_flags & TH_SYN) {
        if (ssn == NULL) {
            ssn = StreamTcpNewSession(p, stt->ssn_pool_id);
            if (ssn == NULL) {
                StatsIncr(tv, stt->counter_tcp_ssn_memcap);
                return -1;
            }

            StatsIncr(tv, stt->counter_tcp_sessions);
        }

        /* set the state */
        StreamTcpPacketSetState(p, ssn, TCP_SYN_SENT);
        SCLogDebug("ssn %p: =~ ssn state is now TCP_SYN_SENT", ssn);

        if (stream_config.async_oneside) {
            SCLogDebug("ssn %p: =~ ASYNC", ssn);
            ssn->flags |= STREAMTCP_FLAG_ASYNC;
        }

        /* set the sequence numbers and window */
        ssn->client.isn = TCP_GET_SEQ(p);
        STREAMTCP_SET_RA_BASE_SEQ(&ssn->client, ssn->client.isn);
        ssn->client.next_seq = ssn->client.isn + 1;

        /* Set the stream timestamp value, if packet has timestamp option
         * enabled. */
        if (TCP_HAS_TS(p)) {
            ssn->client.last_ts = TCP_GET_TSVAL(p);
            SCLogDebug("ssn %p: %02x", ssn, ssn->client.last_ts);

            if (ssn->client.last_ts == 0)
                ssn->client.flags |= STREAMTCP_STREAM_FLAG_ZERO_TIMESTAMP;

            ssn->client.last_pkt_ts = p->ts.tv_sec;
            ssn->client.flags |= STREAMTCP_STREAM_FLAG_TIMESTAMP;
        }

        ssn->server.window = TCP_GET_WINDOW(p);
        if (TCP_HAS_WSCALE(p)) {
            ssn->flags |= STREAMTCP_FLAG_SERVER_WSCALE;
            ssn->server.wscale = TCP_GET_WSCALE(p);
        }

        if (TCP_GET_SACKOK(p) == 1) {
            ssn->flags |= STREAMTCP_FLAG_CLIENT_SACKOK;
            SCLogDebug("ssn %p: SACK permited on SYN packet", ssn);
        }

        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,
                ssn->client.last_ack);

    } else if (p->tcph->th_flags & TH_ACK) {
        if (stream_config.midstream == FALSE)
            return 0;

        if (ssn == NULL) {
            ssn = StreamTcpNewSession(p, stt->ssn_pool_id);
            if (ssn == NULL) {
                StatsIncr(tv, stt->counter_tcp_ssn_memcap);
                return -1;
            }
            StatsIncr(tv, stt->counter_tcp_sessions);
        }
        /* set the state */
        StreamTcpPacketSetState(p, ssn, TCP_ESTABLISHED);
        SCLogDebug("ssn %p: =~ midstream picked ssn state is now "
                "TCP_ESTABLISHED", ssn);

        ssn->flags = STREAMTCP_FLAG_MIDSTREAM;
        ssn->flags |= STREAMTCP_FLAG_MIDSTREAM_ESTABLISHED;
        if (stream_config.async_oneside) {
            SCLogDebug("ssn %p: =~ ASYNC", ssn);
            ssn->flags |= STREAMTCP_FLAG_ASYNC;
        }

        /** window scaling for midstream pickups, we can't do much other
         *  than assume that it's set to the max value: 14 */
        ssn->client.wscale = TCP_WSCALE_MAX;
        ssn->server.wscale = TCP_WSCALE_MAX;

        /* set the sequence numbers and window */
        ssn->client.isn = TCP_GET_SEQ(p) - 1;
        STREAMTCP_SET_RA_BASE_SEQ(&ssn->client, ssn->client.isn);
        ssn->client.next_seq = TCP_GET_SEQ(p) + p->payload_len;
        ssn->client.window = TCP_GET_WINDOW(p) << ssn->client.wscale;
        ssn->client.last_ack = TCP_GET_SEQ(p);
        ssn->client.next_win = ssn->client.last_ack + ssn->client.window;
        SCLogDebug("ssn %p: ssn->client.isn %u, ssn->client.next_seq %u",
                ssn, ssn->client.isn, ssn->client.next_seq);

        ssn->server.isn = TCP_GET_ACK(p) - 1;
        STREAMTCP_SET_RA_BASE_SEQ(&ssn->server, ssn->server.isn);
        ssn->server.next_seq = ssn->server.isn + 1;
        ssn->server.last_ack = TCP_GET_ACK(p);
        ssn->server.next_win = ssn->server.last_ack;

        SCLogDebug("ssn %p: ssn->client.next_win %"PRIu32", "
                "ssn->server.next_win %"PRIu32"", ssn,
                ssn->client.next_win, ssn->server.next_win);
        SCLogDebug("ssn %p: ssn->client.last_ack %"PRIu32", "
                "ssn->server.last_ack %"PRIu32"", ssn,
                ssn->client.last_ack, ssn->server.last_ack);

        /* Set the timestamp value for both streams, if packet has timestamp
         * option enabled.*/
        if (TCP_HAS_TS(p)) {
            ssn->client.last_ts = TCP_GET_TSVAL(p);
            ssn->server.last_ts = TCP_GET_TSECR(p);
            SCLogDebug("ssn %p: ssn->server.last_ts %" PRIu32" "
                    "ssn->client.last_ts %" PRIu32"", ssn,
                    ssn->server.last_ts, ssn->client.last_ts);

            ssn->flags |= STREAMTCP_FLAG_TIMESTAMP;

            ssn->client.last_pkt_ts = p->ts.tv_sec;
            if (ssn->server.last_ts == 0)
                ssn->server.flags |= STREAMTCP_STREAM_FLAG_ZERO_TIMESTAMP;
            if (ssn->client.last_ts == 0)
                ssn->client.flags |= STREAMTCP_STREAM_FLAG_ZERO_TIMESTAMP;

        } else {
            ssn->server.last_ts = 0;
            ssn->client.last_ts = 0;
        }

        StreamTcpReassembleHandleSegment(tv, stt->ra_ctx, ssn, &ssn->client, p, pq);

        ssn->flags |= STREAMTCP_FLAG_SACKOK;
        SCLogDebug("ssn %p: assuming SACK permitted for both sides", ssn);

    } else {
        SCLogDebug("default case");
    }

    return 0;
}
