#!/usr/bin/python
#
# tcpaccept	Trace TCP accept()s.
#		For Linux, uses BCC, eBPF. Embedded C.
#
# USAGE: tcpaccept [-h] [-t] [-p PID]
#
# This uses dynamic tracing of the kernel inet_csk_accept() socket function
# (from tcp_prot.accept), and will need to be modified to match kernel changes.
#
# IPv4 addresses are printed as dotted quads. For IPv6 addresses, the last four
# bytes are printed after "..."; check for future versions with better IPv6
# support.
#
# Copyright (c) 2015 Brendan Gregg.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 13-Oct-2015	Brendan Gregg	Created this.

from __future__ import print_function
from bcc import BPF
import argparse

# arguments
examples = """examples:
    ./tcpaccept           # trace all TCP accept()s
    ./tcpaccept -t        # include timestamps
    ./tcpaccept -p 181    # only trace PID 181
"""
parser = argparse.ArgumentParser(
	description="Trace TCP accepts",
	formatter_class=argparse.RawDescriptionHelpFormatter,
	epilog=examples)
parser.add_argument("-t", "--timestamp", action="store_true",
	help="include timestamp on output")
parser.add_argument("-p", "--pid",
	help="trace this PID only")
args = parser.parse_args()
debug = 0

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

int kretprobe__inet_csk_accept(struct pt_regs *ctx)
{
	struct sock *newsk = (struct sock *)ctx->ax;
	u32 pid = bpf_get_current_pid_tgid();

	if (newsk == NULL)
		return 0;

	// check this is TCP
	u8 protocol = 0;
	// workaround for reading the sk_protocol bitfield:
	bpf_probe_read(&protocol, 1, (void *)((long)&newsk->sk_wmem_queued) - 3);
	if (protocol != IPPROTO_TCP)
		return 0;

	// pull in details
	u16 family = 0, lport = 0;
	u32 saddr = 0, daddr = 0;
	bpf_probe_read(&family, sizeof(family), &newsk->__sk_common.skc_family);
	bpf_probe_read(&lport, sizeof(lport), &newsk->__sk_common.skc_num);
	if (family == AF_INET) {
		bpf_probe_read(&saddr, sizeof(saddr),
		    &newsk->__sk_common.skc_rcv_saddr);
		bpf_probe_read(&daddr, sizeof(daddr),
		    &newsk->__sk_common.skc_daddr);

		// output
		bpf_trace_printk("4 %x %x %d\\n", daddr, saddr, lport);
	} else if (family == AF_INET6) {
		// just grab the last 4 bytes for now
		bpf_probe_read(&saddr, sizeof(saddr),
		    &newsk->__sk_common.skc_v6_rcv_saddr.in6_u.u6_addr32[3]);
		bpf_probe_read(&daddr, sizeof(daddr),
		    &newsk->__sk_common.skc_v6_daddr.in6_u.u6_addr32[3]);

		// output and flip byte order of addresses
		bpf_trace_printk("6 %x %x %d\\n", bpf_ntohl(daddr),
		    bpf_ntohl(saddr), lport);
	}
	// else drop

	return 0;
}
"""

# code substitutions
if args.pid:
	bpf_text = bpf_text.replace('FILTER',
	    'if (pid != %s) { return 0; }' % args.pid)
else:
	bpf_text = bpf_text.replace('FILTER', '')
if debug:
	print(bpf_text)

# initialize BPF
b = BPF(text=bpf_text)

# header
if args.timestamp:
	print("%-9s" % ("TIME(s)"), end="")
print("%-6s %-12s %-2s %-16s %-16s %-4s" % ("PID", "COMM", "IP", "RADDR",
    "LADDR", "LPORT"))

start_ts = 0

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

# format output
while 1:
	(task, pid, cpu, flags, ts, msg) = b.trace_fields()
	(ip_s, raddr_hs, laddr_hs, lport_s) = msg.split(" ")

	if args.timestamp:
		if start_ts == 0:
			start_ts = ts
		print("%-9.3f" % (ts - start_ts), end="")
	print("%-6d %-12.12s %-2s %-16s %-16s %-4s" % (pid, task, ip_s,
	    inet_ntoa(int(raddr_hs, 16)) if ip_s == "4" else "..." + raddr_hs,
	    inet_ntoa(int(laddr_hs, 16)) if ip_s == "4" else "..." + laddr_hs,
	    lport_s))