tcpv4connect.py

#!/usr/bin/python
#
# tcpv4connect	Trace TCP IPv4 connect()s.
#		For Linux, uses BCC, eBPF. Embedded C.
#
# USAGE: tcpv4connect [-h] [-t] [-p PID]
#
# This is provided as a basic example of TCP connection & socket tracing.
#
# All IPv4 connection attempts are traced, even if they ultimately fail.
#
# Copyright (c) 2015 Brendan Gregg.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 15-Oct-2015	Brendan Gregg	Created this.

from __future__ import print_function
from bcc import BPF
from bcc.utils import printb

# define BPF program
bpf_text = """
#include <uapi/linux/ptrace.h>
#include <net/sock.h>
#include <bcc/proto.h>

BPF_HASH(currsock, u32, struct sock *);

int kprobe__tcp_v4_connect(struct pt_regs *ctx, struct sock *sk)
{
	u32 pid = bpf_get_current_pid_tgid();

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

	return 0;
};

int kretprobe__tcp_v4_connect(struct pt_regs *ctx)
{
	int ret = PT_REGS_RC(ctx);
	u32 pid = bpf_get_current_pid_tgid();

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

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

	// pull in details
	struct sock *skp = *skpp;
	u32 saddr = skp->__sk_common.skc_rcv_saddr;
	u32 daddr = skp->__sk_common.skc_daddr;
	u16 dport = skp->__sk_common.skc_dport;

	// output
	bpf_trace_printk("trace_tcp4connect %x %x %d\\n", saddr, daddr, ntohs(dport));

	currsock.delete(&pid);

	return 0;
}
"""

# initialize BPF
b = BPF(text=bpf_text)

# header
print("%-6s %-12s %-16s %-16s %-4s" % ("PID", "COMM", "SADDR", "DADDR",
    "DPORT"))

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

# filter and format output
while 1:
	# Read messages from kernel pipe
	try:
	    (task, pid, cpu, flags, ts, msg) = b.trace_fields()
	    (_tag, saddr_hs, daddr_hs, dport_s) = msg.split(b" ")
	except ValueError:
	    # Ignore messages from other tracers
	    continue
	except KeyboardInterrupt:
	    exit()

	# Ignore messages from other tracers
	if _tag != "trace_tcp4connect":
	    continue

	printb(b"%-6d %-12.12s %-16s %-16s %-4s" % (pid, task,
	    inet_ntoa(int(saddr_hs, 16)),
	    inet_ntoa(int(daddr_hs, 16)),
	    dport_s))