1#!/usr/bin/env python
2#
3# solisten      Trace TCP listen events
4#               For Linux, uses BCC, eBPF. Embedded C.
5#
6# USAGE: solisten.py [-h] [-p PID] [--show-netns]
7#
8# This is provided as a basic example of TCP connection & socket tracing.
9# It could be useful in scenarios where load balancers needs to be updated
10# dynamically as application is fully initialized.
11#
12# All IPv4 listen attempts are traced, even if they ultimately fail or the
13# the listening program is not willing to accept().
14#
15# Copyright (c) 2016 Jean-Tiare Le Bigot.
16# Licensed under the Apache License, Version 2.0 (the "License")
17#
18# 04-Mar-2016	Jean-Tiare Le Bigot	Created this.
19
20import os
21from socket import inet_ntop, AF_INET, AF_INET6, SOCK_STREAM, SOCK_DGRAM
22from struct import pack
23import argparse
24from bcc import BPF
25import ctypes as ct
26
27# Arguments
28examples = """Examples:
29    ./solisten.py              # Stream socket listen
30    ./solisten.py -p 1234      # Stream socket listen for specified PID only
31    ./solisten.py --netns 4242 # " for the specified network namespace ID only
32    ./solisten.py --show-netns # Show network ns ID (useful for containers)
33"""
34
35parser = argparse.ArgumentParser(
36    description="Stream sockets listen",
37    formatter_class=argparse.RawDescriptionHelpFormatter,
38    epilog=examples)
39parser.add_argument("--show-netns", action="store_true",
40    help="show network namespace")
41parser.add_argument("-p", "--pid", default=0, type=int,
42    help="trace this PID only")
43parser.add_argument("-n", "--netns", default=0, type=int,
44    help="trace this Network Namespace only")
45parser.add_argument("--ebpf", action="store_true",
46    help=argparse.SUPPRESS)
47
48
49# BPF Program
50bpf_text = """
51#include <net/net_namespace.h>
52#include <bcc/proto.h>
53#pragma clang diagnostic push
54#pragma clang diagnostic ignored "-Wenum-conversion"
55#include <net/inet_sock.h>
56#pragma clang diagnostic pop
57
58// Common structure for UDP/TCP IPv4/IPv6
59struct listen_evt_t {
60    u64 ts_us;
61    u64 pid_tgid;
62    u64 backlog;
63    u64 netns;
64    u64 proto;    // familiy << 16 | type
65    u64 lport;    // use only 16 bits
66    u64 laddr[2]; // IPv4: store in laddr[0]
67    char task[TASK_COMM_LEN];
68};
69BPF_PERF_OUTPUT(listen_evt);
70
71// Send an event for each IPv4 listen with PID, bound address and port
72int kprobe__inet_listen(struct pt_regs *ctx, struct socket *sock, int backlog)
73{
74        // cast types. Intermediate cast not needed, kept for readability
75        struct sock *sk = sock->sk;
76        struct inet_sock *inet = (struct inet_sock *)sk;
77
78        // Built event for userland
79        struct listen_evt_t evt = {
80            .ts_us = bpf_ktime_get_ns() / 1000,
81            .backlog = backlog,
82        };
83
84        // Get process comm. Needs LLVM >= 3.7.1
85        // see https://github.com/iovisor/bcc/issues/393
86        bpf_get_current_comm(evt.task, TASK_COMM_LEN);
87
88        // Get socket IP family
89        u16 family = sk->__sk_common.skc_family;
90        evt.proto = family << 16 | SOCK_STREAM;
91
92        // Get PID
93        evt.pid_tgid = bpf_get_current_pid_tgid();
94
95        ##FILTER_PID##
96
97        // Get port
98        evt.lport = inet->inet_sport;
99        evt.lport = ntohs(evt.lport);
100
101        // Get network namespace id, if kernel supports it
102#ifdef CONFIG_NET_NS
103        evt.netns = sk->__sk_common.skc_net.net->ns.inum;
104#else
105        evt.netns = 0;
106#endif
107
108        ##FILTER_NETNS##
109
110        // Get IP
111        if (family == AF_INET) {
112            evt.laddr[0] = inet->inet_rcv_saddr;
113        } else if (family == AF_INET6) {
114            bpf_probe_read(evt.laddr, sizeof(evt.laddr),
115                           sk->__sk_common.skc_v6_rcv_saddr.in6_u.u6_addr32);
116        }
117
118        // Send event to userland
119        listen_evt.perf_submit(ctx, &evt, sizeof(evt));
120
121        return 0;
122};
123"""
124
125# event data
126TASK_COMM_LEN = 16      # linux/sched.h
127class ListenEvt(ct.Structure):
128    _fields_ = [
129        ("ts_us", ct.c_ulonglong),
130        ("pid_tgid", ct.c_ulonglong),
131        ("backlog", ct.c_ulonglong),
132        ("netns", ct.c_ulonglong),
133        ("proto", ct.c_ulonglong),
134        ("lport", ct.c_ulonglong),
135        ("laddr", ct.c_ulonglong * 2),
136        ("task", ct.c_char * TASK_COMM_LEN)
137    ]
138
139    # TODO: properties to unpack protocol / ip / pid / tgid ...
140
141# Format output
142def event_printer(show_netns):
143    def print_event(cpu, data, size):
144        # Decode event
145        event = ct.cast(data, ct.POINTER(ListenEvt)).contents
146
147        pid = event.pid_tgid & 0xffffffff
148        proto_family = event.proto & 0xff
149        proto_type = event.proto >> 16 & 0xff
150
151        if proto_family == SOCK_STREAM:
152            protocol = "TCP"
153        elif proto_family == SOCK_DGRAM:
154            protocol = "UDP"
155        else:
156            protocol = "UNK"
157
158        address = ""
159        if proto_type == AF_INET:
160            protocol += "v4"
161            address = inet_ntop(AF_INET, pack("I", event.laddr[0]))
162        elif proto_type == AF_INET6:
163            address = inet_ntop(AF_INET6, event.laddr)
164            protocol += "v6"
165
166        # Display
167        if show_netns:
168            print("%-6d %-12.12s %-12s %-6s %-8s %-5s %-39s" % (
169                pid, event.task, event.netns, protocol, event.backlog,
170                event.lport, address,
171            ))
172        else:
173            print("%-6d %-12.12s %-6s %-8s %-5s %-39s" % (
174                pid, event.task, protocol, event.backlog,
175                event.lport, address,
176            ))
177
178    return print_event
179
180if __name__ == "__main__":
181    # Parse arguments
182    args = parser.parse_args()
183
184    pid_filter = ""
185    netns_filter = ""
186
187    if args.pid:
188        pid_filter = "if (evt.pid_tgid != %d) return 0;" % args.pid
189    if args.netns:
190        netns_filter = "if (evt.netns != %d) return 0;" % args.netns
191
192    bpf_text = bpf_text.replace("##FILTER_PID##", pid_filter)
193    bpf_text = bpf_text.replace("##FILTER_NETNS##", netns_filter)
194
195    if args.ebpf:
196        print(bpf_text)
197        exit()
198
199    # Initialize BPF
200    b = BPF(text=bpf_text)
201    b["listen_evt"].open_perf_buffer(event_printer(args.show_netns))
202
203    # Print headers
204    if args.show_netns:
205        print("%-6s %-12s %-12s %-6s %-8s %-5s %-39s" %
206              ("PID", "COMM", "NETNS", "PROTO", "BACKLOG", "PORT", "ADDR"))
207    else:
208        print("%-6s %-12s %-6s %-8s %-5s %-39s" %
209              ("PID", "COMM", "PROTO", "BACKLOG", "PORT", "ADDR"))
210
211    # Read events
212    while 1:
213        b.perf_buffer_poll()
214