问如何从多个IP数据包中重建TCP流？

EN

typedef struct _tcp_flow_t {
    guint32 base_seq;   /* base seq number (used by relative sequence numbers)
                 * or 0 if not yet known.
                 */
    tcp_unacked_t *segments;
    guint32 fin;        /* frame number of the final FIN */
    guint32 lastack;    /* last seen ack */
    nstime_t lastacktime;   /* Time of the last ack packet */
    guint32 lastnondupack;  /* frame number of last seen non dupack */
    guint32 dupacknum;  /* dupack number */
    guint32 nextseq;    /* highest seen nextseq */
    guint32 maxseqtobeacked;/* highest seen continuous seq number (without hole in the stream) from the fwd party,
                 * this is the maximum seq number that can be acked by the rev party in normal case.
                 * If the rev party sends an ACK beyond this seq number it indicates TCP_A_ACK_LOST_PACKET contition */
    guint32 nextseqframe;   /* frame number for segment with highest
                 * sequence number
                 */

/* Attach process info to a flow */
/* XXX - We depend on the TCP dissector finding the conversation first */
void
add_tcp_process_info(guint32 frame_num, address *local_addr, address *remote_addr, guint16 local_port, guint16 remote_port, guint32 uid, guint32 pid, gchar *username, gchar *command) {
    conversation_t *conv;
    struct tcp_analysis *tcpd;
    tcp_flow_t *flow = NULL;

    conv = find_conversation(frame_num, local_addr, remote_addr, PT_TCP, local_port, remote_port, 0);
    if (!conv) {
        return;
    }

/*
 * Given two address/port pairs for a packet, search for a conversation
 * containing packets between those address/port pairs.  Returns NULL if
 * not found.
 *
 * We try to find the most exact match that we can, and then proceed to
 * try wildcard matches on the "addr_b" and/or "port_b" argument if a more
 * exact match failed.
 * ...
 */
conversation_t *
find_conversation(const guint32 frame_num, const address *addr_a, const address *addr_b, const port_type ptype,
    const guint32 port_a, const guint32 port_b, const guint options)
{
   conversation_t *conversation;

   /*
    * First try an exact match, if we have two addresses and ports.
    */
   if (!(options & (NO_ADDR_B|NO_PORT_B))) {

#include <linux/netfilter.h>
#include <libipq.h>

ipq_packet_msg_t *m = ipq_get_packet(buf);

struct iphdr *ip = (struct iphdr*) m->payload;

struct tcphdr *tcp = (struct tcphdr*) (m->payload + (4 * ip->ihl));

int port = htons(tcp->dest);        

status = ipq_set_verdict(h, m->packet_id,
                          NF_ACCEPT, 0, NULL);
if (status < 0)
        die(h);