Commit 30656b09 authored by Zhang Chen's avatar Zhang Chen Committed by Jason Wang
Browse files

filter-rewriter: rewrite tcp packet to keep secondary connection 



We will rewrite tcp packet secondary received and sent.
When colo guest is a tcp server.

Firstly, client start a tcp handshake. the packet's seq=client_seq,
ack=0,flag=SYN. COLO primary guest get this pkt and mirror(filter-mirror)
to secondary guest, secondary get it use filter-redirector.
Then,primary guest response pkt
(seq=primary_seq,ack=client_seq+1,flag=ACK|SYN).
secondary guest response pkt
(seq=secondary_seq,ack=client_seq+1,flag=ACK|SYN).
In here,we use filter-rewriter save the secondary_seq to it's tcp connection.
Finally handshake,client send pkt
(seq=client_seq+1,ack=primary_seq+1,flag=ACK).
Here,filter-rewriter can get primary_seq, and rewrite ack from primary_seq+1
to secondary_seq+1, recalculate checksum. So the secondary tcp connection
kept good.

When we send/recv packet.
client send pkt(seq=client_seq+1+data_len,ack=primary_seq+1,flag=ACK|PSH).
filter-rewriter rewrite ack and send to secondary guest.

primary guest response pkt
(seq=primary_seq+1,ack=client_seq+1+data_len,flag=ACK)
secondary guest response pkt
(seq=secondary_seq+1,ack=client_seq+1+data_len,flag=ACK)
we rewrite secondary guest seq from secondary_seq+1 to primary_seq+1.
So tcp connection kept good.

In code We use offset( = secondary_seq - primary_seq )
to rewrite seq or ack.
handle_primary_tcp_pkt: tcp_pkt->th_ack += offset;
handle_secondary_tcp_pkt: tcp_pkt->th_seq -= offset;

Signed-off-by: default avatarZhang Chen <zhangchen.fnst@cn.fujitsu.com>
Signed-off-by: default avatarLi Zhijian <lizhijian@cn.fujitsu.com>
Signed-off-by: default avatarWen Congyang <wency@cn.fujitsu.com>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
parent afe46124

net/colo.c

+2 −0
Original line number Diff line number Diff line
@@ -134,6 +134,8 @@ Connection *connection_new(ConnectionKey *key) 


    conn->ip_proto = key->ip_proto;

    conn->processing = false;

    conn->offset = 0;

    conn->syn_flag = 0;

    g_queue_init(&conn->primary_list);

    g_queue_init(&conn->secondary_list);

net/colo.h

+7 −0
Original line number Diff line number Diff line
@@ -62,6 +62,13 @@ typedef struct Connection { 
    /* flag to enqueue unprocessed_connections */

    bool processing;

    uint8_t ip_proto;

    /* offset = secondary_seq - primary_seq */

    tcp_seq  offset;

    /*

     * we use this flag update offset func

     * run once in independent tcp connection

     */

    int syn_flag;

} Connection;



uint32_t connection_key_hash(const void *opaque);

net/filter-rewriter.c

+110 −2
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ 
 */



#include "qemu/osdep.h"

#include "trace.h"

#include "net/colo.h"

#include "net/filter.h"

#include "net/net.h"
@@ -58,6 +59,93 @@ static int is_tcp_packet(Packet *pkt) 
    }

}



/* handle tcp packet from primary guest */

static int handle_primary_tcp_pkt(NetFilterState *nf,

                                  Connection *conn,

                                  Packet *pkt)

{

    struct tcphdr *tcp_pkt;



    tcp_pkt = (struct tcphdr *)pkt->transport_header;

    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));

        trace_colo_filter_rewriter_pkt_info(__func__, sdebug, ddebug,

                    ntohl(tcp_pkt->th_seq), ntohl(tcp_pkt->th_ack),

                    tcp_pkt->th_flags);

        trace_colo_filter_rewriter_conn_offset(conn->offset);

        g_free(sdebug);

        g_free(ddebug);

    }



    if (((tcp_pkt->th_flags & (TH_ACK | TH_SYN)) == TH_SYN)) {

        /*

         * we use this flag update offset func

         * run once in independent tcp connection

         */

        conn->syn_flag = 1;

    }



    if (((tcp_pkt->th_flags & (TH_ACK | TH_SYN)) == TH_ACK)) {

        if (conn->syn_flag) {

            /*

             * offset = secondary_seq - primary seq

             * ack packet sent by guest from primary node,

             * so we use th_ack - 1 get primary_seq

             */

            conn->offset -= (ntohl(tcp_pkt->th_ack) - 1);

            conn->syn_flag = 0;

        }

        /* handle packets to the secondary from the primary */

        tcp_pkt->th_ack = htonl(ntohl(tcp_pkt->th_ack) + conn->offset);



        net_checksum_calculate((uint8_t *)pkt->data, pkt->size);

    }



    return 0;

}



/* handle tcp packet from secondary guest */

static int handle_secondary_tcp_pkt(NetFilterState *nf,

                                    Connection *conn,

                                    Packet *pkt)

{

    struct tcphdr *tcp_pkt;



    tcp_pkt = (struct tcphdr *)pkt->transport_header;



    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));

        trace_colo_filter_rewriter_pkt_info(__func__, sdebug, ddebug,

                    ntohl(tcp_pkt->th_seq), ntohl(tcp_pkt->th_ack),

                    tcp_pkt->th_flags);

        trace_colo_filter_rewriter_conn_offset(conn->offset);

        g_free(sdebug);

        g_free(ddebug);

    }



    if (((tcp_pkt->th_flags & (TH_ACK | TH_SYN)) == (TH_ACK | TH_SYN))) {

        /*

         * save offset = secondary_seq and then

         * in handle_primary_tcp_pkt make offset

         * = secondary_seq - primary_seq

         */

        conn->offset = ntohl(tcp_pkt->th_seq);

    }



    if ((tcp_pkt->th_flags & (TH_ACK | TH_SYN)) == TH_ACK) {

        /* handle packets to the primary from the secondary*/

        tcp_pkt->th_seq = htonl(ntohl(tcp_pkt->th_seq) - conn->offset);



        net_checksum_calculate((uint8_t *)pkt->data, pkt->size);

    }



    return 0;

}



static ssize_t colo_rewriter_receive_iov(NetFilterState *nf,

                                         NetClientState *sender,

                                         unsigned flags,
@@ -97,10 +185,30 @@ static ssize_t colo_rewriter_receive_iov(NetFilterState *nf, 


        if (sender == nf->netdev) {

            /* 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;

            }

        }

    }

trace-events

+5 −0
Original line number Diff line number Diff line
@@ -150,6 +150,11 @@ colo_compare_ip_info(int psize, const char *sta, const char *stb, int ssize, con 
colo_old_packet_check_found(int64_t old_time) "%" PRId64

colo_compare_miscompare(void) ""



# net/filter-rewriter.c

colo_filter_rewriter_debug(void) ""

colo_filter_rewriter_pkt_info(const char *func, const char *src, const char *dst, uint32_t seq, uint32_t ack, uint32_t flag) "%s: src/dst: %s/%s p: seq/ack=%u/%u  flags=%x\n"

colo_filter_rewriter_conn_offset(uint32_t offset) ": offset=%u\n"



### Guest events, keep at bottom



# @vaddr: Access' virtual address.