How to show accepted TCP connections on FreeBSD using Dtrace

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As of 2013-06-19, the DTrace TCP provider is not available in FreeBSD, so we need a workaround.

#!/usr/sbin/dtrace -s

fbt::tcp_usr_accept:entry
{
    this->inp = (struct inpcb*)(args[0]->so_pcb);
   this->inp_lport = this->inp->inp_inc.inc_ie.ie_lport;
   this->inp_fport = this->inp->inp_inc.inc_ie.ie_fport;
   printf("%d.%d.%d.%d:%d -> ", 
       ((unsigned char *)&this->inp->inp_inc.inc_ie.ie_dependfaddr.ie46_foreign.ia46_addr4.s_addr)[0],
     ((unsigned char *)&this->inp->inp_inc.inc_ie.ie_dependfaddr.ie46_foreign.ia46_addr4.s_addr)[1],
     ((unsigned char *)&this->inp->inp_inc.inc_ie.ie_dependfaddr.ie46_foreign.ia46_addr4.s_addr)[2],
     ((unsigned char *)&this->inp->inp_inc.inc_ie.ie_dependfaddr.ie46_foreign.ia46_addr4.s_addr)[3],
     ntohs(this->inp_fport)
  );

  printf("%d.%d.%d.%d:%d\n", 
        ((unsigned char *)&this->inp->inp_inc.inc_ie.ie_dependladdr.ie46_local.ia46_addr4.s_addr)[0],
       ((unsigned char *)&this->inp->inp_inc.inc_ie.ie_dependladdr.ie46_local.ia46_addr4.s_addr)[1],
       ((unsigned char *)&this->inp->inp_inc.inc_ie.ie_dependladdr.ie46_local.ia46_addr4.s_addr)[2],
       ((unsigned char *)&this->inp->inp_inc.inc_ie.ie_dependladdr.ie46_local.ia46_addr4.s_addr)[3],
       ntohs(this->inp_lport)
  );
}

Sample output:

  2  20578             tcp_usr_accept:entry 10.0.0.13:34529 -> 10.0.0.10:80
  2  20578             tcp_usr_accept:entry 10.0.0.13:34533 -> 10.0.0.10:80
  2  20578             tcp_usr_accept:entry 10.0.0.10:34553 -> 10.0.0.12:3306
  2  20578             tcp_usr_accept:entry 10.0.0.13:34555 -> 10.0.0.10:80
  2  20578             tcp_usr_accept:entry 10.0.0.10:34557 -> 10.0.0.12:3306
  3  20578             tcp_usr_accept:entry 10.0.0.13:34461 -> 10.0.0.10:80
  3  20578             tcp_usr_accept:entry 10.0.0.10:34474 -> 10.0.0.12:3306
  3  20578             tcp_usr_accept:entry 10.0.0.13:34504 -> 10.0.0.10:80
  3  20578             tcp_usr_accept:entry 10.0.0.13:34514 -> 10.0.0.10:80
  3  20578             tcp_usr_accept:entry 10.0.0.13:34518 -> 10.0.0.10:80

System:

FreeBSD hostmaster1.example.com 9.1-STABLE FreeBSD 9.1-STABLE #0 r248486: Thu Jun 13 00:23:59 CEST 2013     root@hostmaster1.example.com:/usr/obj/usr/src/sys/HOSTMASTER1  amd64

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