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#! /usr/bin/python3
# @lint-avoid-python-3-compatibility-imports
#
# tcpconnect Trace TCP connect()s.
# For Linux, uses BCC, eBPF. Embedded C.
#
# USAGE: tcpconnect [-h] [-c] [-t] [-p PID] [-P PORT [PORT ...]] [-4 | -6]
#
# All connection attempts are traced, even if they ultimately fail.
#
# This uses dynamic tracing of kernel functions, and will need to be updated
# to match kernel changes.
#
# Copyright (c) 2015 Brendan Gregg.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 25-Sep-2015 Brendan Gregg Created this.
# 14-Feb-2016 " " Switch to bpf_perf_output.
# 09-Jan-2019 Takuma Kume Support filtering by UID
# 30-Jul-2019 Xiaozhou Liu Count connects.
# 07-Oct-2020 Nabil Schear Correlate connects with DNS responses
# 08-Mar-2021 Suresh Kumar Added LPORT option
from __future__ import print_function
from bcc import BPF
from bcc.containers import filter_by_containers
from bcc.utils import printb
import argparse
from socket import inet_ntop, ntohs, AF_INET, AF_INET6
from struct import pack
from time import sleep
from datetime import datetime
# arguments
examples = """examples:
./tcpconnect # trace all TCP connect()s
./tcpconnect -t # include timestamps
./tcpconnect -d # include DNS queries associated with connects
./tcpconnect -p 181 # only trace PID 181
./tcpconnect -P 80 # only trace port 80
./tcpconnect -P 80,81 # only trace port 80 and 81
./tcpconnect -4 # only trace IPv4 family
./tcpconnect -6 # only trace IPv6 family
./tcpconnect -U # include UID
./tcpconnect -u 1000 # only trace UID 1000
./tcpconnect -c # count connects per src ip and dest ip/port
./tcpconnect -L # include LPORT while printing outputs
./tcpconnect --cgroupmap mappath # only trace cgroups in this BPF map
./tcpconnect --mntnsmap mappath # only trace mount namespaces in the map
"""
parser = argparse.ArgumentParser(
description="Trace TCP connects",
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("-P", "--port",
help="comma-separated list of destination ports to trace.")
group = parser.add_mutually_exclusive_group()
group.add_argument("-4", "--ipv4", action="store_true",
help="trace IPv4 family only")
group.add_argument("-6", "--ipv6", action="store_true",
help="trace IPv6 family only")
parser.add_argument("-L", "--lport", action="store_true",
help="include LPORT on output")
parser.add_argument("-U", "--print-uid", action="store_true",
help="include UID on output")
parser.add_argument("-u", "--uid",
help="trace this UID only")
parser.add_argument("-c", "--count", action="store_true",
help="count connects per src ip and dest ip/port")
parser.add_argument("--cgroupmap",
help="trace cgroups in this BPF map only")
parser.add_argument("--mntnsmap",
help="trace mount namespaces in this BPF map only")
parser.add_argument("-d", "--dns", action="store_true",
help="include likely DNS query associated with each connect")
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>
BPF_HASH(currsock, u32, struct sock *);
// separate data structs for ipv4 and ipv6
struct ipv4_data_t {
u64 ts_us;
u32 pid;
u32 uid;
u32 saddr;
u32 daddr;
u64 ip;
u16 lport;
u16 dport;
char task[TASK_COMM_LEN];
};
BPF_PERF_OUTPUT(ipv4_events);
struct ipv6_data_t {
u64 ts_us;
u32 pid;
u32 uid;
unsigned __int128 saddr;
unsigned __int128 daddr;
u64 ip;
u16 lport;
u16 dport;
char task[TASK_COMM_LEN];
};
BPF_PERF_OUTPUT(ipv6_events);
// separate flow keys per address family
struct ipv4_flow_key_t {
u32 saddr;
u32 daddr;
u16 dport;
};
BPF_HASH(ipv4_count, struct ipv4_flow_key_t);
struct ipv6_flow_key_t {
unsigned __int128 saddr;
unsigned __int128 daddr;
u16 dport;
};
BPF_HASH(ipv6_count, struct ipv6_flow_key_t);
int trace_connect_entry(struct pt_regs *ctx, struct sock *sk)
{
if (container_should_be_filtered()) {
return 0;
}
u64 pid_tgid = bpf_get_current_pid_tgid();
u32 pid = pid_tgid >> 32;
u32 tid = pid_tgid;
FILTER_PID
u32 uid = bpf_get_current_uid_gid();
FILTER_UID
// stash the sock ptr for lookup on return
currsock.update(&tid, &sk);
return 0;
};
static int trace_connect_return(struct pt_regs *ctx, short ipver)
{
int ret = PT_REGS_RC(ctx);
u64 pid_tgid = bpf_get_current_pid_tgid();
u32 pid = pid_tgid >> 32;
u32 tid = pid_tgid;
struct sock **skpp;
skpp = currsock.lookup(&tid);
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(&tid);
return 0;
}
// pull in details
struct sock *skp = *skpp;
u16 lport = skp->__sk_common.skc_num;
u16 dport = skp->__sk_common.skc_dport;
FILTER_PORT
FILTER_FAMILY
if (ipver == 4) {
IPV4_CODE
} else /* 6 */ {
IPV6_CODE
}
currsock.delete(&tid);
return 0;
}
int trace_connect_v4_return(struct pt_regs *ctx)
{
return trace_connect_return(ctx, 4);
}
int trace_connect_v6_return(struct pt_regs *ctx)
{
return trace_connect_return(ctx, 6);
}
"""
struct_init = {'ipv4':
{'count':
"""
struct ipv4_flow_key_t flow_key = {};
flow_key.saddr = skp->__sk_common.skc_rcv_saddr;
flow_key.daddr = skp->__sk_common.skc_daddr;
flow_key.dport = ntohs(dport);
ipv4_count.increment(flow_key);""",
'trace':
"""
struct ipv4_data_t data4 = {.pid = pid, .ip = ipver};
data4.uid = bpf_get_current_uid_gid();
data4.ts_us = bpf_ktime_get_ns() / 1000;
data4.saddr = skp->__sk_common.skc_rcv_saddr;
data4.daddr = skp->__sk_common.skc_daddr;
data4.lport = lport;
data4.dport = ntohs(dport);
bpf_get_current_comm(&data4.task, sizeof(data4.task));
ipv4_events.perf_submit(ctx, &data4, sizeof(data4));"""
},
'ipv6':
{'count':
"""
struct ipv6_flow_key_t flow_key = {};
bpf_probe_read_kernel(&flow_key.saddr, sizeof(flow_key.saddr),
skp->__sk_common.skc_v6_rcv_saddr.in6_u.u6_addr32);
bpf_probe_read_kernel(&flow_key.daddr, sizeof(flow_key.daddr),
skp->__sk_common.skc_v6_daddr.in6_u.u6_addr32);
flow_key.dport = ntohs(dport);
ipv6_count.increment(flow_key);""",
'trace':
"""
struct ipv6_data_t data6 = {.pid = pid, .ip = ipver};
data6.uid = bpf_get_current_uid_gid();
data6.ts_us = bpf_ktime_get_ns() / 1000;
bpf_probe_read_kernel(&data6.saddr, sizeof(data6.saddr),
skp->__sk_common.skc_v6_rcv_saddr.in6_u.u6_addr32);
bpf_probe_read_kernel(&data6.daddr, sizeof(data6.daddr),
skp->__sk_common.skc_v6_daddr.in6_u.u6_addr32);
data6.lport = lport;
data6.dport = ntohs(dport);
bpf_get_current_comm(&data6.task, sizeof(data6.task));
ipv6_events.perf_submit(ctx, &data6, sizeof(data6));"""
}
}
# This defines an additional BPF program that instruments udp_recvmsg system
# call to locate DNS response packets on UDP port 53. When these packets are
# located, the data is copied to user-space where python will parse them with
# dnslib.
#
# uses a percpu array of length 1 to store the dns_data_t off the stack to
# allow for a maximum DNS packet length of 512 bytes.
dns_bpf_text = """
#include <net/inet_sock.h>
#define MAX_PKT 512
struct dns_data_t {
u8 pkt[MAX_PKT];
};
BPF_PERF_OUTPUT(dns_events);
// store msghdr pointer captured on syscall entry to parse on syscall return
BPF_HASH(tbl_udp_msg_hdr, u64, struct msghdr *);
// single element per-cpu array to hold the current event off the stack
BPF_PERCPU_ARRAY(dns_data,struct dns_data_t,1);
int trace_udp_recvmsg(struct pt_regs *ctx)
{
__u64 pid_tgid = bpf_get_current_pid_tgid();
struct sock *sk = (struct sock *)PT_REGS_PARM1(ctx);
struct inet_sock *is = inet_sk(sk);
// only grab port 53 packets, 13568 is ntohs(53)
if (is->inet_dport == 13568) {
struct msghdr *msghdr = (struct msghdr *)PT_REGS_PARM2(ctx);
tbl_udp_msg_hdr.update(&pid_tgid, &msghdr);
}
return 0;
}
int trace_udp_ret_recvmsg(struct pt_regs *ctx)
{
__u64 pid_tgid = bpf_get_current_pid_tgid();
u32 zero = 0;
struct msghdr **msgpp = tbl_udp_msg_hdr.lookup(&pid_tgid);
if (msgpp == 0)
return 0;
struct msghdr *msghdr = (struct msghdr *)*msgpp;
if (msghdr->msg_iter.TYPE_FIELD != ITER_IOVEC)
goto delete_and_return;
int copied = (int)PT_REGS_RC(ctx);
if (copied < 0)
goto delete_and_return;
size_t buflen = (size_t)copied;
if (buflen > msghdr->msg_iter.iov->iov_len)
goto delete_and_return;
if (buflen > MAX_PKT)
buflen = MAX_PKT;
struct dns_data_t *data = dns_data.lookup(&zero);
if (!data) // this should never happen, just making the verifier happy
return 0;
void *iovbase = msghdr->msg_iter.iov->iov_base;
bpf_probe_read(data->pkt, buflen, iovbase);
dns_events.perf_submit(ctx, data, buflen);
delete_and_return:
tbl_udp_msg_hdr.delete(&pid_tgid);
return 0;
}
#include <uapi/linux/udp.h>
int trace_udpv6_recvmsg(struct pt_regs *ctx)
{
struct sk_buff *skb = (struct sk_buff *)PT_REGS_PARM2(ctx);
struct udphdr *hdr = (void*)skb->head + skb->transport_header;
struct dns_data_t *event;
int zero = 0;
void *data;
/* hex(53) = 0x0035, htons(0x0035) = 0x3500 */
if (hdr->source != 0x3500)
return 0;
/* skip UDP header */
data = skb->data + 8;
event = dns_data.lookup(&zero);
if (!event)
return 0;
bpf_probe_read(event->pkt, sizeof(event->pkt), data);
dns_events.perf_submit(ctx, event, sizeof(*event));
return 0;
}
"""
if args.count and args.dns:
print("Error: you may not specify -d/--dns with -c/--count.")
exit()
# code substitutions
if args.count:
bpf_text = bpf_text.replace("IPV4_CODE", struct_init['ipv4']['count'])
bpf_text = bpf_text.replace("IPV6_CODE", struct_init['ipv6']['count'])
else:
bpf_text = bpf_text.replace("IPV4_CODE", struct_init['ipv4']['trace'])
bpf_text = bpf_text.replace("IPV6_CODE", struct_init['ipv6']['trace'])
if args.pid:
bpf_text = bpf_text.replace('FILTER_PID',
'if (pid != %s) { return 0; }' % args.pid)
if args.port:
dports = [int(dport) for dport in args.port.split(',')]
dports_if = ' && '.join(['dport != %d' % ntohs(dport) for dport in dports])
bpf_text = bpf_text.replace('FILTER_PORT',
'if (%s) { currsock.delete(&tid); return 0; }' % dports_if)
if args.ipv4:
bpf_text = bpf_text.replace('FILTER_FAMILY',
'if (ipver != 4) { return 0; }')
elif args.ipv6:
bpf_text = bpf_text.replace('FILTER_FAMILY',
'if (ipver != 6) { return 0; }')
if args.uid:
bpf_text = bpf_text.replace('FILTER_UID',
'if (uid != %s) { return 0; }' % args.uid)
bpf_text = filter_by_containers(args) + bpf_text
bpf_text = bpf_text.replace('FILTER_PID', '')
bpf_text = bpf_text.replace('FILTER_PORT', '')
bpf_text = bpf_text.replace('FILTER_FAMILY', '')
bpf_text = bpf_text.replace('FILTER_UID', '')
if args.dns:
if BPF.kernel_struct_has_field(b'iov_iter', b'iter_type') == 1:
dns_bpf_text = dns_bpf_text.replace('TYPE_FIELD', 'iter_type')
else:
dns_bpf_text = dns_bpf_text.replace('TYPE_FIELD', 'type')
bpf_text += dns_bpf_text
if debug or args.ebpf:
print(bpf_text)
if args.ebpf:
exit()
# process event
def print_ipv4_event(cpu, data, size):
event = b["ipv4_events"].event(data)
global start_ts
if args.timestamp:
if start_ts == 0:
start_ts = event.ts_us
printb(b"%-9.3f" % ((float(event.ts_us) - start_ts) / 1000000), nl="")
if args.print_uid:
printb(b"%-6d" % event.uid, nl="")
dest_ip = inet_ntop(AF_INET, pack("I", event.daddr)).encode()
if args.lport:
printb(b"%-7d %-12.12s %-2d %-16s %-6d %-16s %-6d %s" % (event.pid,
event.task, event.ip,
inet_ntop(AF_INET, pack("I", event.saddr)).encode(), event.lport,
dest_ip, event.dport, print_dns(dest_ip)))
else:
printb(b"%-7d %-12.12s %-2d %-16s %-16s %-6d %s" % (event.pid,
event.task, event.ip,
inet_ntop(AF_INET, pack("I", event.saddr)).encode(),
dest_ip, event.dport, print_dns(dest_ip)))
def print_ipv6_event(cpu, data, size):
event = b["ipv6_events"].event(data)
global start_ts
if args.timestamp:
if start_ts == 0:
start_ts = event.ts_us
printb(b"%-9.3f" % ((float(event.ts_us) - start_ts) / 1000000), nl="")
if args.print_uid:
printb(b"%-6d" % event.uid, nl="")
dest_ip = inet_ntop(AF_INET6, event.daddr).encode()
if args.lport:
printb(b"%-7d %-12.12s %-2d %-16s %-6d %-16s %-6d %s" % (event.pid,
event.task, event.ip,
inet_ntop(AF_INET6, event.saddr).encode(), event.lport,
dest_ip, event.dport, print_dns(dest_ip)))
else:
printb(b"%-7d %-12.12s %-2d %-16s %-16s %-6d %s" % (event.pid,
event.task, event.ip,
inet_ntop(AF_INET6, event.saddr).encode(),
dest_ip, event.dport, print_dns(dest_ip)))
def depict_cnt(counts_tab, l3prot='ipv4'):
for k, v in sorted(counts_tab.items(),
key=lambda counts: counts[1].value, reverse=True):
depict_key = ""
if l3prot == 'ipv4':
depict_key = "%-25s %-25s %-20s" % \
((inet_ntop(AF_INET, pack('I', k.saddr))),
inet_ntop(AF_INET, pack('I', k.daddr)), k.dport)
else:
depict_key = "%-25s %-25s %-20s" % \
((inet_ntop(AF_INET6, k.saddr)),
inet_ntop(AF_INET6, k.daddr), k.dport)
print("%s %-10d" % (depict_key, v.value))
def print_dns(dest_ip):
if not args.dns:
return b""
dnsname, timestamp = dns_cache.get(dest_ip, (None, None))
if timestamp is not None:
diff = datetime.now() - timestamp
diff = float(diff.seconds) * 1000 + float(diff.microseconds) / 1000
else:
diff = 0
if dnsname is None:
dnsname = b"No DNS Query"
if dest_ip == b"127.0.0.1" or dest_ip == b"::1":
dnsname = b"localhost"
retval = b"%s" % dnsname
if diff > DELAY_DNS:
retval += b" (%.3fms)" % diff
return retval
if args.dns:
try:
import dnslib
from cachetools import TTLCache
except ImportError:
print("Error: The python packages dnslib and cachetools are required "
"to use the -d/--dns option.")
print("Install this package with:")
print("\t$ pip3 install dnslib cachetools")
print(" or")
print("\t$ sudo apt-get install python3-dnslib python3-cachetools "
"(on Ubuntu 18.04+)")
exit(1)
# 24 hours
DEFAULT_TTL = 86400
# Cache Size in entries
DNS_CACHE_SIZE = 10240
# delay in ms in which to warn users of long delay between the query
# and the connect that used the IP
DELAY_DNS = 100
dns_cache = TTLCache(maxsize=DNS_CACHE_SIZE, ttl=DEFAULT_TTL)
# process event
def save_dns(cpu, data, size):
event = b["dns_events"].event(data)
payload = event.pkt[:size]
# pass the payload to dnslib for parsing
dnspkt = dnslib.DNSRecord.parse(payload)
# lets only look at responses
if dnspkt.header.qr != 1:
return
# must be some questions in there
if dnspkt.header.q != 1:
return
# make sure there are answers
if dnspkt.header.a == 0 and dnspkt.header.aa == 0:
return
# lop off the trailing .
question = ("%s" % dnspkt.q.qname)[:-1].encode('utf-8')
for answer in dnspkt.rr:
# skip all but A and AAAA records
if answer.rtype == 1 or answer.rtype == 28:
dns_cache[str(answer.rdata).encode('utf-8')] = (question,
datetime.now())
# initialize BPF
b = BPF(text=bpf_text)
b.attach_kprobe(event="tcp_v4_connect", fn_name="trace_connect_entry")
b.attach_kprobe(event="tcp_v6_connect", fn_name="trace_connect_entry")
b.attach_kretprobe(event="tcp_v4_connect", fn_name="trace_connect_v4_return")
b.attach_kretprobe(event="tcp_v6_connect", fn_name="trace_connect_v6_return")
if args.dns:
b.attach_kprobe(event="udp_recvmsg", fn_name="trace_udp_recvmsg")
b.attach_kretprobe(event="udp_recvmsg", fn_name="trace_udp_ret_recvmsg")
b.attach_kprobe(event="udpv6_queue_rcv_one_skb", fn_name="trace_udpv6_recvmsg")
print("Tracing connect ... Hit Ctrl-C to end")
if args.count:
try:
while True:
sleep(99999999)
except KeyboardInterrupt:
pass
# header
print("\n%-25s %-25s %-20s %-10s" % (
"LADDR", "RADDR", "RPORT", "CONNECTS"))
depict_cnt(b["ipv4_count"])
depict_cnt(b["ipv6_count"], l3prot='ipv6')
# read events
else:
# header
if args.timestamp:
print("%-9s" % ("TIME(s)"), end="")
if args.print_uid:
print("%-6s" % ("UID"), end="")
if args.lport:
print("%-7s %-12s %-2s %-16s %-6s %-16s %-6s" % ("PID", "COMM", "IP", "SADDR",
"LPORT", "DADDR", "DPORT"), end="")
else:
print("%-7s %-12s %-2s %-16s %-16s %-6s" % ("PID", "COMM", "IP", "SADDR",
"DADDR", "DPORT"), end="")
if args.dns:
print(" QUERY")
else:
print()
start_ts = 0
# read events
b["ipv4_events"].open_perf_buffer(print_ipv4_event)
b["ipv6_events"].open_perf_buffer(print_ipv6_event)
if args.dns:
b["dns_events"].open_perf_buffer(save_dns)
while True:
try:
b.perf_buffer_poll()
except KeyboardInterrupt:
exit()
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