tcptracer.py

#!/usr/bin/python
#
# tcpv4tracer   Trace TCP connections.
#               For Linux, uses BCC, eBPF. Embedded C.
#
# USAGE: tcpv4tracer [-h] [-v] [-p PID] [-N NETNS]
#
# You should generally try to avoid writing long scripts that measure multiple
# functions and walk multiple kernel structures, as they will be a burden to
# maintain as the kernel changes.
# The following code should be replaced, and simplified, when static TCP probes
# exist.
#
# Copyright 2017 Kinvolk GmbH
#
# Licensed under the Apache License, Version 2.0 (the "License")
from __future__ import print_function
from bcc import BPF

import argparse as ap
import ctypes
from socket import inet_ntop, AF_INET, AF_INET6
from struct import pack

parser = ap.ArgumentParser(description="Trace TCP connections",
                           formatter_class=ap.RawDescriptionHelpFormatter)
parser.add_argument("-p", "--pid", default=0, type=int,
                    help="trace this PID only")
parser.add_argument("-N", "--netns", default=0, type=int,
                    help="trace this Network Namespace only")
parser.add_argument("-v", "--verbose", action="store_true",
                    help="include Network Namespace in the output")
args = parser.parse_args()

bpf_text = """
#include <uapi/linux/ptrace.h>
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wtautological-compare"
#include <net/sock.h>
#pragma clang diagnostic pop
#include <net/inet_sock.h>
#include <net/net_namespace.h>
#include <bcc/proto.h>

#define TCP_EVENT_TYPE_CONNECT 1
#define TCP_EVENT_TYPE_ACCEPT  2
#define TCP_EVENT_TYPE_CLOSE   3

struct tcp_ipv4_event_t {
    u32 type;
    u32 pid;
    char comm[TASK_COMM_LEN];
    u8 ip;
    u32 saddr;
    u32 daddr;
    u16 sport;
    u16 dport;
    u32 netns;
};
BPF_PERF_OUTPUT(tcp_ipv4_event);

struct tcp_ipv6_event_t {
    u32 type;
    u32 pid;
    char comm[TASK_COMM_LEN];
    u8 ip;
    unsigned __int128 saddr;
    unsigned __int128 daddr;
    u16 sport;
    u16 dport;
    u32 netns;
};
BPF_PERF_OUTPUT(tcp_ipv6_event);

// tcp_set_state doesn't run in the context of the process that initiated the
// connection so we need to store a map TUPLE -> PID to send the right PID on
// the event
struct ipv4_tuple_t {
    u32 saddr;
    u32 daddr;
    u16 sport;
    u16 dport;
    u32 netns;
};

struct ipv6_tuple_t {
    unsigned __int128 saddr;
    unsigned __int128 daddr;
    u16 sport;
    u16 dport;
    u32 netns;
};

struct pid_comm_t {
    u64 pid;
    char comm[TASK_COMM_LEN];
};

BPF_HASH(tuplepid_ipv4, struct ipv4_tuple_t, struct pid_comm_t);
BPF_HASH(tuplepid_ipv6, struct ipv6_tuple_t, struct pid_comm_t);

BPF_HASH(connectsock, u64, struct sock *);

static int read_ipv4_tuple(struct ipv4_tuple_t *tuple, struct sock *skp)
{
  u32 saddr = 0, daddr = 0, net_ns_inum = 0;
  u16 sport = 0, dport = 0;
  possible_net_t skc_net;

  bpf_probe_read(&saddr, sizeof(saddr), &skp->__sk_common.skc_rcv_saddr);
  bpf_probe_read(&daddr, sizeof(daddr), &skp->__sk_common.skc_daddr);
  bpf_probe_read(&sport, sizeof(sport),
                 &((struct inet_sock *)skp)->inet_sport);
  bpf_probe_read(&dport, sizeof(dport), &skp->__sk_common.skc_dport);
#ifdef CONFIG_NET_NS
  bpf_probe_read(&skc_net, sizeof(skc_net), &skp->__sk_common.skc_net);
  bpf_probe_read(&net_ns_inum, sizeof(net_ns_inum), &skc_net.net->ns.inum);
#else
  net_ns_inum = 0;
#endif

  ##FILTER_NETNS##

  tuple->saddr = saddr;
  tuple->daddr = daddr;
  tuple->sport = sport;
  tuple->dport = dport;
  tuple->netns = net_ns_inum;

  // if addresses or ports are 0, ignore
  if (saddr == 0 || daddr == 0 || sport == 0 || dport == 0) {
      return 0;
  }

  return 1;
}

static int read_ipv6_tuple(struct ipv6_tuple_t *tuple, struct sock *skp)
{
  u32 net_ns_inum = 0;
  u16 sport = 0, dport = 0;
  unsigned __int128 saddr = 0, daddr = 0;
  possible_net_t skc_net;

  bpf_probe_read(&sport, sizeof(sport),
                 &((struct inet_sock *)skp)->inet_sport);
  bpf_probe_read(&dport, sizeof(dport), &skp->__sk_common.skc_dport);
  bpf_probe_read(&saddr, sizeof(saddr),
                 &skp->__sk_common.skc_v6_rcv_saddr.in6_u.u6_addr32);
  bpf_probe_read(&daddr, sizeof(daddr),
                 &skp->__sk_common.skc_v6_daddr.in6_u.u6_addr32);
#ifdef CONFIG_NET_NS
  bpf_probe_read(&skc_net, sizeof(skc_net), &skp->__sk_common.skc_net);
  bpf_probe_read(&net_ns_inum, sizeof(net_ns_inum), &skc_net.net->ns.inum);
#else
  net_ns_inum = 0;
#endif

  ##FILTER_NETNS##

  tuple->saddr = saddr;
  tuple->daddr = daddr;
  tuple->sport = sport;
  tuple->dport = dport;
  tuple->netns = net_ns_inum;

  // if addresses or ports are 0, ignore
  if (saddr == 0 || daddr == 0 || sport == 0 || dport == 0) {
      return 0;
  }

  return 1;
}

static bool check_family(struct sock *sk, u16 expected_family) {
  u64 zero = 0;
  u16 family = 0;

  bpf_probe_read(&family, sizeof(family), &sk->__sk_common.skc_family);

  return family == expected_family;
}

int trace_connect_v4_entry(struct pt_regs *ctx, struct sock *sk)
{
  u64 pid = bpf_get_current_pid_tgid();

  ##FILTER_PID##

  // stash the sock ptr for lookup on return
  connectsock.update(&pid, &sk);

  return 0;
}

int trace_connect_v4_return(struct pt_regs *ctx)
{
  int ret = PT_REGS_RC(ctx);
  u64 pid = bpf_get_current_pid_tgid();

  struct sock **skpp;
  skpp = connectsock.lookup(&pid);
  if (skpp == 0) {
      return 0;       // missed entry
  }

  connectsock.delete(&pid);

  if (ret != 0) {
      // failed to send SYNC packet, may not have populated
      // socket __sk_common.{skc_rcv_saddr, ...}
      return 0;
  }

  // pull in details
  struct sock *skp = *skpp;
  struct ipv4_tuple_t t = { };
  if (!read_ipv4_tuple(&t, skp)) {
      return 0;
  }

  struct pid_comm_t p = { };
  p.pid = pid;
  bpf_get_current_comm(&p.comm, sizeof(p.comm));

  tuplepid_ipv4.update(&t, &p);

  return 0;
}

int trace_connect_v6_entry(struct pt_regs *ctx, struct sock *sk)
{
  u64 pid = bpf_get_current_pid_tgid();

  ##FILTER_PID##

  // stash the sock ptr for lookup on return
  connectsock.update(&pid, &sk);

  return 0;
}

int trace_connect_v6_return(struct pt_regs *ctx)
{
  int ret = PT_REGS_RC(ctx);
  u64 pid = bpf_get_current_pid_tgid();

  struct sock **skpp;
  skpp = connectsock.lookup(&pid);
  if (skpp == 0) {
      return 0;       // missed entry
  }

  connectsock.delete(&pid);

  if (ret != 0) {
      // failed to send SYNC packet, may not have populated
      // socket __sk_common.{skc_rcv_saddr, ...}
      return 0;
  }

  // pull in details
  struct sock *skp = *skpp;
  struct ipv6_tuple_t t = { };
  if (!read_ipv6_tuple(&t, skp)) {
      return 0;
  }

  struct pid_comm_t p = { };
  p.pid = pid;
  bpf_get_current_comm(&p.comm, sizeof(p.comm));

  tuplepid_ipv6.update(&t, &p);

  return 0;
}

int trace_tcp_set_state_entry(struct pt_regs *ctx, struct sock *sk, int state)
{
  if (state != TCP_ESTABLISHED && state != TCP_CLOSE) {
      return 0;
  }

  struct sock *skp;
  bpf_probe_read(&skp, sizeof(struct sock *), &sk);

  u8 ipver = 0;
  if (check_family(skp, AF_INET)) {
      ipver = 4;
      struct ipv4_tuple_t t = { };
      if (!read_ipv4_tuple(&t, skp)) {
          return 0;
      }

      if (state == TCP_CLOSE) {
          tuplepid_ipv4.delete(&t);
          return 0;
      }

      struct pid_comm_t *p;
      p = tuplepid_ipv4.lookup(&t);
      if (p == 0) {
          return 0;       // missed entry
      }

      struct tcp_ipv4_event_t evt4 = { };
      evt4.type = TCP_EVENT_TYPE_CONNECT;
      evt4.pid = p->pid >> 32;
      evt4.ip = ipver;
      evt4.saddr = t.saddr;
      evt4.daddr = t.daddr;
      evt4.sport = ntohs(t.sport);
      evt4.dport = ntohs(t.dport);
      evt4.netns = t.netns;

      int i;
      for (i = 0; i < TASK_COMM_LEN; i++) {
          evt4.comm[i] = p->comm[i];
      }

      tcp_ipv4_event.perf_submit(ctx, &evt4, sizeof(evt4));
      tuplepid_ipv4.delete(&t);
  } else if (check_family(skp, AF_INET6)) {
      ipver = 6;
      struct ipv6_tuple_t t = { };
      if (!read_ipv6_tuple(&t, skp)) {
          return 0;
      }

      if (state == TCP_CLOSE) {
          tuplepid_ipv6.delete(&t);
          return 0;
      }

      struct pid_comm_t *p;
      p = tuplepid_ipv6.lookup(&t);
      if (p == 0) {
          return 0;       // missed entry
      }

      struct tcp_ipv6_event_t evt6 = { };
      evt6.type = TCP_EVENT_TYPE_CONNECT;
      evt6.pid = p->pid >> 32;
      evt6.ip = ipver;
      evt6.saddr = t.saddr;
      evt6.daddr = t.daddr;
      evt6.sport = ntohs(t.sport);
      evt6.dport = ntohs(t.dport);
      evt6.netns = t.netns;

      int i;
      for (i = 0; i < TASK_COMM_LEN; i++) {
          evt6.comm[i] = p->comm[i];
      }

      tcp_ipv6_event.perf_submit(ctx, &evt6, sizeof(evt6));
      tuplepid_ipv6.delete(&t);
  }
  // else drop

  return 0;
}

int trace_close_entry(struct pt_regs *ctx, struct sock *sk)
{
  u64 pid = bpf_get_current_pid_tgid();

  ##FILTER_PID##

  // pull in details
  struct sock *skp;
  bpf_probe_read(&skp, sizeof(struct sock *), &sk);

  u8 oldstate = 0;
  bpf_probe_read(&oldstate, sizeof(oldstate), (u8 *)&skp->sk_state);
  // Don't generate close events for connections that were never
  // established in the first place.
  if (oldstate == TCP_SYN_SENT ||
      oldstate == TCP_SYN_RECV ||
      oldstate == TCP_NEW_SYN_RECV)
      return 0;

  u8 ipver = 0;
  if (check_family(skp, AF_INET)) {
      ipver = 4;
      struct ipv4_tuple_t t = { };
      if (!read_ipv4_tuple(&t, skp)) {
          return 0;
      }

      struct tcp_ipv4_event_t evt4 = { };
      evt4.type = TCP_EVENT_TYPE_CLOSE;
      evt4.pid = pid >> 32;
      evt4.ip = ipver;
      evt4.saddr = t.saddr;
      evt4.daddr = t.daddr;
      evt4.sport = ntohs(t.sport);
      evt4.dport = ntohs(t.dport);
      evt4.netns = t.netns;
      bpf_get_current_comm(&evt4.comm, sizeof(evt4.comm));

      tcp_ipv4_event.perf_submit(ctx, &evt4, sizeof(evt4));
  } else if (check_family(skp, AF_INET6)) {
      ipver = 6;
      struct ipv6_tuple_t t = { };
      if (!read_ipv6_tuple(&t, skp)) {
          return 0;
      }

      struct tcp_ipv6_event_t evt6 = { };
      evt6.type = TCP_EVENT_TYPE_CLOSE;
      evt6.pid = pid >> 32;
      evt6.ip = ipver;
      evt6.saddr = t.saddr;
      evt6.daddr = t.daddr;
      evt6.sport = ntohs(t.sport);
      evt6.dport = ntohs(t.dport);
      evt6.netns = t.netns;
      bpf_get_current_comm(&evt6.comm, sizeof(evt6.comm));

      tcp_ipv6_event.perf_submit(ctx, &evt6, sizeof(evt6));
  }
  // else drop

  return 0;
};

int trace_accept_return(struct pt_regs *ctx)
{
  struct sock *newsk = (struct sock *)PT_REGS_RC(ctx);
  u64 pid = bpf_get_current_pid_tgid();

  ##FILTER_PID##

  if (newsk == NULL) {
      return 0;
  }

  // pull in details
  u16 lport = 0, dport = 0;
  u32 net_ns_inum = 0;
  u8 ipver = 0;

  bpf_probe_read(&dport, sizeof(dport), &newsk->__sk_common.skc_dport);
  bpf_probe_read(&lport, sizeof(lport), &newsk->__sk_common.skc_num);

  // Get network namespace id, if kernel supports it
#ifdef CONFIG_NET_NS
  possible_net_t skc_net;
  bpf_probe_read(&skc_net, sizeof(skc_net), &newsk->__sk_common.skc_net);
  bpf_probe_read(&net_ns_inum, sizeof(net_ns_inum), &skc_net.net->ns.inum);
#else
  net_ns_inum = 0;
#endif

  ##FILTER_NETNS##

  if (check_family(newsk, AF_INET)) {
      ipver = 4;

      struct tcp_ipv4_event_t evt4 = { 0 };

      evt4.type = TCP_EVENT_TYPE_ACCEPT;
      evt4.netns = net_ns_inum;
      evt4.pid = pid >> 32;
      evt4.ip = ipver;

      bpf_probe_read(&evt4.saddr, sizeof(evt4.saddr),
                     &newsk->__sk_common.skc_rcv_saddr);
      bpf_probe_read(&evt4.daddr, sizeof(evt4.daddr),
                     &newsk->__sk_common.skc_daddr);

      evt4.sport = lport;
      evt4.dport = ntohs(dport);
      bpf_get_current_comm(&evt4.comm, sizeof(evt4.comm));

      // do not send event if IP address is 0.0.0.0 or port is 0
      if (evt4.saddr != 0 && evt4.daddr != 0 &&
          evt4.sport != 0 && evt4.dport != 0) {
          tcp_ipv4_event.perf_submit(ctx, &evt4, sizeof(evt4));
      }
  } else if (check_family(newsk, AF_INET6)) {
      ipver = 6;

      struct tcp_ipv6_event_t evt6 = { 0 };

      evt6.type = TCP_EVENT_TYPE_ACCEPT;
      evt6.netns = net_ns_inum;
      evt6.pid = pid >> 32;
      evt6.ip = ipver;

      bpf_probe_read(&evt6.saddr, sizeof(evt6.saddr),
                     &newsk->__sk_common.skc_v6_rcv_saddr.in6_u.u6_addr32);
      bpf_probe_read(&evt6.daddr, sizeof(evt6.daddr),
                     &newsk->__sk_common.skc_v6_daddr.in6_u.u6_addr32);

      evt6.sport = lport;
      evt6.dport = ntohs(dport);
      bpf_get_current_comm(&evt6.comm, sizeof(evt6.comm));

      // do not send event if IP address is 0.0.0.0 or port is 0
      if (evt6.saddr != 0 && evt6.daddr != 0 &&
          evt6.sport != 0 && evt6.dport != 0) {
          tcp_ipv6_event.perf_submit(ctx, &evt6, sizeof(evt6));
      }
  }
  // else drop

  return 0;
}
"""

TASK_COMM_LEN = 16   # linux/sched.h


class TCPIPV4Evt(ctypes.Structure):
    _fields_ = [
            ("type", ctypes.c_uint),
            ("pid", ctypes.c_uint),
            ("comm", ctypes.c_char * TASK_COMM_LEN),
            ("ip", ctypes.c_ubyte),
            ("saddr", ctypes.c_uint),
            ("daddr", ctypes.c_uint),
            ("sport", ctypes.c_ushort),
            ("dport", ctypes.c_ushort),
            ("netns", ctypes.c_uint)
    ]


class TCPIPV6Evt(ctypes.Structure):
    _fields_ = [
            ("type", ctypes.c_uint),
            ("pid", ctypes.c_uint),
            ("comm", ctypes.c_char * TASK_COMM_LEN),
            ("ip", ctypes.c_ubyte),
            ("saddr", (ctypes.c_ulong * 2)),
            ("daddr", (ctypes.c_ulong * 2)),
            ("sport", ctypes.c_ushort),
            ("dport", ctypes.c_ushort),
            ("netns", ctypes.c_uint)
    ]


verbose_types = {"C": "connect", "A": "accept",
                 "X": "close", "U": "unknown"}


def print_ipv4_event(cpu, data, size):
    event = ctypes.cast(data, ctypes.POINTER(TCPIPV4Evt)).contents
    if event.type == 1:
        type_str = "C"
    elif event.type == 2:
        type_str = "A"
    elif event.type == 3:
        type_str = "X"
    else:
        type_str = "U"

    if args.verbose:
        print("%-12s " % (verbose_types[type_str]), end="")
    else:
        print("%-2s " % (type_str), end="")

    print("%-6d %-16s %-2d %-16s %-16s %-6d %-6d" %
          (event.pid, event.comm.decode('utf-8'),
           event.ip,
           inet_ntop(AF_INET, pack("I", event.saddr)),
           inet_ntop(AF_INET, pack("I", event.daddr)),
           event.sport,
           event.dport), end="")
    if args.verbose and not args.netns:
        print(" %-8d" % event.netns)
    else:
        print()


def print_ipv6_event(cpu, data, size):
    event = ctypes.cast(data, ctypes.POINTER(TCPIPV6Evt)).contents
    if event.type == 1:
        type_str = "C"
    elif event.type == 2:
        type_str = "A"
    elif event.type == 3:
        type_str = "X"
    else:
        type_str = "U"

    if args.verbose:
        print("%-12s " % (verbose_types[type_str]), end="")
    else:
        print("%-2s " % (type_str), end="")

    print("%-6d %-16s %-2d %-16s %-16s %-6d %-6d" %
          (event.pid, event.comm.decode('utf-8'),
           event.ip,
           "["+inet_ntop(AF_INET6, event.saddr)+"]",
           "["+inet_ntop(AF_INET6, event.daddr)+"]",
           event.sport,
           event.dport), end="")
    if args.verbose and not args.netns:
        print(" %-8d" % event.netns)
    else:
        print()


pid_filter = ""
netns_filter = ""

if args.pid:
    pid_filter = 'if (pid >> 32 != %d) { return 0; }' % args.pid
if args.netns:
    netns_filter = 'if (net_ns_inum != %d) { return 0; }' % args.netns

bpf_text = bpf_text.replace('##FILTER_PID##', pid_filter)
bpf_text = bpf_text.replace('##FILTER_NETNS##', netns_filter)

# initialize BPF
b = BPF(text=bpf_text)
b.attach_kprobe(event="tcp_v4_connect", fn_name="trace_connect_v4_entry")
b.attach_kretprobe(event="tcp_v4_connect", fn_name="trace_connect_v4_return")
b.attach_kprobe(event="tcp_v6_connect", fn_name="trace_connect_v6_entry")
b.attach_kretprobe(event="tcp_v6_connect", fn_name="trace_connect_v6_return")
b.attach_kprobe(event="tcp_set_state", fn_name="trace_tcp_set_state_entry")
b.attach_kprobe(event="tcp_close", fn_name="trace_close_entry")
b.attach_kretprobe(event="inet_csk_accept", fn_name="trace_accept_return")

print("Tracing TCP established connections. Ctrl-C to end.")

# header
if args.verbose:
    print("%-12s %-6s %-16s %-2s %-16s %-16s %-6s %-7s" % ("TYPE",
          "PID", "COMM", "IP", "SADDR", "DADDR", "SPORT", "DPORT"), end="")
    if not args.netns:
        print("%-8s" % "NETNS", end="")
    print()
else:
    print("%-2s %-6s %-16s %-2s %-16s %-16s %-6s %-6s" %
          ("T", "PID", "COMM", "IP", "SADDR", "DADDR", "SPORT", "DPORT"))


def inet_ntoa(addr):
    dq = ''
    for i in range(0, 4):
        dq = dq + str(addr & 0xff)
        if (i != 3):
            dq = dq + '.'
        addr = addr >> 8
    return dq


b["tcp_ipv4_event"].open_perf_buffer(print_ipv4_event)
b["tcp_ipv6_event"].open_perf_buffer(print_ipv6_event)
while True:
    b.kprobe_poll()