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Filename : tcp_retransmission.stp
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#!/usr/bin/stap

#################################################################
# tcp_retransmit.stp
# Author: Yang Bingwu (detailyang) <detailyang@gmail.com>
# This systemtap script will prints the tcp retransmission packet
#################################################################

global record%

probe begin {
    log("Printing tcp retransmission")
}

probe kernel.function("tcp_retransmit_skb") {
    rto = tcp_get_info_rto($sk)
    saddr   = format_ipaddr(__ip_sock_saddr($sk), __ip_sock_family($sk))
    daddr   = format_ipaddr(__ip_sock_daddr($sk), __ip_sock_family($sk))
    sport   = __tcp_sock_sport($sk)
    dport   = __tcp_sock_dport($sk)
    lastrto = record[saddr, sport, daddr, dport]
    state = tcp_ts_get_info_state($sk)

    if (lastrto != rto) {
        if (lastrto) {
            printf("%s:%d => %s:%d STATE:%s RTO:%d -> %d (ms)\n", saddr, sport,
                daddr, dport, tcp_sockstate_str(state), lastrto/1000, rto/1000)
        } else {
            printf("%s:%d => %s:%d STATE:%s RTO:%d (ms)\n", saddr, sport,
                daddr, dport, tcp_sockstate_str(state), rto/1000)
        }
    }

    record[saddr, sport, daddr, dport] = rto
}