tcpconnect.bt

#!/usr/bin/env bpftrace
// tcpconnect.bt  Trace TCP connect()s.
//                For Linux, uses bpftrace and eBPF.
//
// All connection attempts are traced, even if they ultimately fail.
//
// This uses dynamic tracing of kernel functions, and will need to be updated
// to match kernel changes.
//
// Example of usage:
//
// # ./tcpconnect.bt
// TIME     PID      COMM             SADDR          SPORT  DADDR          DPORT
// 00:36:45 1798396  agent            127.0.0.1      5001   10.229.20.82   56114
// 00:36:45 1798396  curl             127.0.0.1      10255  10.229.20.82   56606
// 00:36:45 3949059  nginx            127.0.0.1      8000   127.0.0.1      37780
//
//
// This output shows three connections, one from a "agent" process, one from
// "curl", and one from "nginx". The output details shows the IP version, source
// address, source socket port, destination address, and destination port. This traces attempted
// connections: these may have failed.
//
// The overhead of this tool should be negligible, since it is only tracing the
// kernel functions performing connect. It is not tracing every packet and then
// filtering.
//
// This is a bpftrace version of the bcc tool of the same name.
//
// Copyright (c) 2018 Dale Hamel.
//
// 23-Nov-2018	Dale Hamel	created this.

#ifndef BPFTRACE_HAVE_BTF
#include <linux/socket.h>
#include <net/sock.h>
#else
// BTF provides the types, we just need to define AF_INET and AF_INET6.
// These are Linux ABI defines, and are not architecture-specific.
// With BTF, this allows tcpconnect.bt to work without glibc headers:
#define AF_INET   2 /* IPv4 */
#define AF_INET6 10 /* IPv6 */
#endif

BEGIN
{
  printf("Tracing tcp connections. Hit Ctrl-C to end.\n");
  printf("%-8s %-8s %-16s ", "TIME", "PID", "COMM");
  printf("%-39s %-6s %-39s %-6s\n", "SADDR", "SPORT", "DADDR", "DPORT");
}

kprobe:tcp_connect
{
  let $daddr;
  let $saddr;
  $sk = (struct sock *)arg0;
  $inet_family = $sk.__sk_common.skc_family;

  if ($inet_family == AF_INET || $inet_family == AF_INET6) {
    if ($inet_family == AF_INET) {
      $daddr = ntop($sk.__sk_common.skc_daddr);
      $saddr = ntop($sk.__sk_common.skc_rcv_saddr);
    } else {
      $daddr = ntop($sk.__sk_common.skc_v6_daddr.in6_u.u6_addr8);
      $saddr = ntop($sk.__sk_common.skc_v6_rcv_saddr.in6_u.u6_addr8);
    }
    $lport = $sk.__sk_common.skc_num;
    $dport = $sk.__sk_common.skc_dport;

    // Destination port is big endian, it must be flipped
    $dport = bswap($dport);

    time("%H:%M:%S ");
    printf("%-8d %-16s ", pid, comm);
    printf("%-39s %-6d %-39s %-6d\n", $saddr, $lport, $daddr, $dport);
  }
}