Manual Pages  — DTRACE_SCTP

dtrace_sctp – a DTrace provider for tracing events related to the sctp(4) protocol

The DTrace sctp provider allows users to trace events in the sctp(4) protocol implementation. This provider is similar to the dtrace_ip(4) and dtrace_udp(4) providers, but additionally contains probes corresponding to protocol events at a level higher than packet reception and transmission.

The sctp:cwnd::() probes track changes in the congestion window on a netp. The sctp:rwnd::() probes track changes in the receiver window for an assoc. The sctp:flightsize:net:val() probe tracks changes in the flight size on a net or assoc and the sctp:flightsize:assoc:val() probe provides the total flight version.

The arguments of all sctp probes except for sctp:cwnd::rtt*() and sctp::assoc:val() are the Vtag for this end, the port number of the local side, the pointer to struct sctp_nets *changing, the old value of the cwnd, and the new value of the cwnd.

The arguments of sctp:::val() are similar to the above except the fourth argument is the up/down amount.

The sctp:cwnd::rtt*() probe arguments are a bitmap of Vtag << 32 | localport << 16 | remoteport, a bitmap of obw | nbw, a bitmap of bwrtt | newrtt, flight, and a bitmap of (cwnd << 32) | point << 16 | retval(0/1).

The sctp:cwnd::init() probe fires when a remotely-initiated active SCTP open succeeds. At this point the new connection is in the ESTABLISHED state, and the probe arguments expose the headers associated with the final ACK of the four-way handshake.

The sctp:::send() and sctp:::receive() probes fire when the host sends or receives an SCTP packet, respectively. As with the dtrace_udp(4) provider, sctp probes fire only for packets sent by or to the local host; forwarded packets are handled in the IP layer and are only visible to the dtrace_ip(4) provider.

The sctp:::state-change() probe fires upon local SCTP association state transitions. Its first, third and fifth arguments are currently always NULL. Its last argument describes the from-state in the transition, and the to-state can be obtained from args[3]->sctps_state.

#pragma D option quiet
#pragma D option switchrate=10hz

dtrace:::BEGIN
{
        printf(" %3s %15s:%-5s      %15s:%-5s0, "CPU",
            "LADDR", "LPORT", "RADDR", "RPORT");
}

sctp:::send
{
        printf(" %3d %16s:%-5d -> %16s:%-5d0, cpu,
            args[2]->ip_saddr, args[4]->sctp_sport,
            args[2]->ip_daddr, args[4]->sctp_dport);
}

sctp:::receive
{
        printf(" %3d %16s:%-5d <- %16s:%-5d0, cpu,
            args[2]->ip_daddr, args[4]->sctp_dport,
            args[2]->ip_saddr, args[4]->sctp_sport);
}

#pragma D option quiet
#pragma D option switchrate=10

int last[int];

dtrace:::BEGIN
{
        printf(" %3s %12s  %-25s    %-25s0,
            "CPU", "DELTA(us)", "OLD", "NEW");
}

sctp:::state-change
/ last[args[1]->cs_cid] /
{
        this->elapsed = (timestamp - last[args[1]->cs_cid]) / 1000;
        printf(" %3d %12d  %-25s -> %-25s0, cpu, this->elapsed,
            sctp_state_string[args[5]->sctps_state],
            sctp_state_string[args[3]->sctps_state]);
        last[args[1]->cs_cid] = timestamp;
}

sctp:::state-change
/ last[args[1]->cs_cid] == 0 /
{
        printf(" %3d %12s  %-25s -> %-25s0, cpu, "-",
            sctp_state_string[args[5]->sctps_state],
            sctp_state_string[args[3]->sctps_state]);
        last[args[1]->cs_cid] = timestamp;
}

dtrace(1), dtrace_ip(4), dtrace_udp(4), dtrace_udplite(4), sctp(4), SDT(9)