tcpaccept.py

#!/usr/bin/python
# @lint-avoid-python-3-compatibility-imports
#
# 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.
#
# Copyright (c) 2015 Brendan Gregg.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 13-Oct-2015   Brendan Gregg   Created this.
# 14-Feb-2016      "      "     Switch to bpf_perf_output.

from __future__ import print_function
from bcc import BPF
from socket import inet_ntop, AF_INET, AF_INET6
from struct import pack
import argparse
import ctypes as ct

# 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")
parser.add_argument("--ebpf", action="store_true",
    help=argparse.SUPPRESS)
args = parser.parse_args()
debug = 0

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

// separate data structs for ipv4 and ipv6
struct ipv4_data_t {
    // XXX: switch some to u32's when supported
    u64 ts_us;
    u64 pid;
    u64 saddr;
    u64 daddr;
    u64 ip;
    u64 lport;
    char task[TASK_COMM_LEN];
};
BPF_PERF_OUTPUT(ipv4_events);

struct ipv6_data_t {
    u64 ts_us;
    u64 pid;
    unsigned __int128 saddr;
    unsigned __int128 daddr;
    u64 ip;
    u64 lport;
    char task[TASK_COMM_LEN];
};
BPF_PERF_OUTPUT(ipv6_events);

int kretprobe__inet_csk_accept(struct pt_regs *ctx)
{
    struct sock *newsk = (struct sock *)PT_REGS_RC(ctx);
    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;
    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) {
        struct ipv4_data_t data4 = {.pid = pid, .ip = 4};
        data4.ts_us = bpf_ktime_get_ns() / 1000;
        bpf_probe_read(&data4.saddr, sizeof(u32),
            &newsk->__sk_common.skc_rcv_saddr);
        bpf_probe_read(&data4.daddr, sizeof(u32),
            &newsk->__sk_common.skc_daddr);
        data4.lport = lport;
        bpf_get_current_comm(&data4.task, sizeof(data4.task));
        ipv4_events.perf_submit(ctx, &data4, sizeof(data4));

    } else if (family == AF_INET6) {
        struct ipv6_data_t data6 = {.pid = pid, .ip = 6};
        data6.ts_us = bpf_ktime_get_ns() / 1000;
        bpf_probe_read(&data6.saddr, sizeof(data6.saddr),
            &newsk->__sk_common.skc_v6_rcv_saddr.in6_u.u6_addr32);
        bpf_probe_read(&data6.daddr, sizeof(data6.daddr),
            &newsk->__sk_common.skc_v6_daddr.in6_u.u6_addr32);
        data6.lport = lport;
        bpf_get_current_comm(&data6.task, sizeof(data6.task));
        ipv6_events.perf_submit(ctx, &data6, sizeof(data6));
    }
    // 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 or args.ebpf:
    print(bpf_text)
    if args.ebpf:
        exit()

# event data
TASK_COMM_LEN = 16      # linux/sched.h

class Data_ipv4(ct.Structure):
    _fields_ = [
        ("ts_us", ct.c_ulonglong),
        ("pid", ct.c_ulonglong),
        ("saddr", ct.c_ulonglong),
        ("daddr", ct.c_ulonglong),
        ("ip", ct.c_ulonglong),
        ("lport", ct.c_ulonglong),
        ("task", ct.c_char * TASK_COMM_LEN)
    ]

class Data_ipv6(ct.Structure):
    _fields_ = [
        ("ts_us", ct.c_ulonglong),
        ("pid", ct.c_ulonglong),
        ("saddr", (ct.c_ulonglong * 2)),
        ("daddr", (ct.c_ulonglong * 2)),
        ("ip", ct.c_ulonglong),
        ("lport", ct.c_ulonglong),
        ("task", ct.c_char * TASK_COMM_LEN)
    ]

# process event
def print_ipv4_event(cpu, data, size):
    event = ct.cast(data, ct.POINTER(Data_ipv4)).contents
    global start_ts
    if args.timestamp:
        if start_ts == 0:
            start_ts = event.ts_us
        print("%-9.3f" % ((float(event.ts_us) - start_ts) / 1000000), end="")
    print("%-6d %-12.12s %-2d %-16s %-16s %-4d" % (event.pid,
        event.task.decode(), event.ip,
        inet_ntop(AF_INET, pack("I", event.daddr)),
        inet_ntop(AF_INET, pack("I", event.saddr)), event.lport))

def print_ipv6_event(cpu, data, size):
    event = ct.cast(data, ct.POINTER(Data_ipv6)).contents
    global start_ts
    if args.timestamp:
        if start_ts == 0:
            start_ts = event.ts_us
        print("%-9.3f" % ((float(event.ts_us) - start_ts) / 1000000), end="")
    print("%-6d %-12.12s %-2d %-16s %-16s %-4d" % (event.pid,
        event.task.decode(), event.ip, inet_ntop(AF_INET6, event.daddr),
        inet_ntop(AF_INET6, event.saddr), event.lport))

# 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

# read events
b["ipv4_events"].open_perf_buffer(print_ipv4_event)
b["ipv6_events"].open_perf_buffer(print_ipv6_event)
while 1:
    b.perf_buffer_poll()