tcpv4connect

README.md

@@ -72,6 +72,7 @@ Tools:
 - tools/[opensnoop](tools/opensnoop): Trace open() syscalls. [Examples](tools/opensnoop_example.txt).
 - tools/[pidpersec](tools/pidpersec): Count new processes (via fork). [Examples](tools/pidpersec_example.txt).
 - tools/[syncsnoop](tools/syncsnoop): Trace sync() syscall. [Examples](tools/syncsnoop_example.txt).
+- tools/[tcpv4connect](tools/tcpv4connect): Trace TCP IPv4 active connections. [Examples](tools/tcpv4connect_example.txt).
 - tools/[vfscount](tools/vfscount) tools/[vfscount.c](tools/vfscount.c): Count VFS calls. [Examples](tools/vfscount_example.txt).
 - tools/[vfsstat](tools/vfsstat) tools/[vfsstat.c](tools/vfsstat.c): Count some VFS calls, with column output. [Examples](tools/vfsstat_example.txt).
 

man/man8/tcpv4connect.8

+.TH tcpv4connect 8  "2015-08-25" "USER COMMANDS"
+.SH NAME
+tcpv4connect \- Trace TCP IPv4 active connections. Uses Linux eBPF/bcc.
+.SH SYNOPSIS
+.B tcpv4connect [\-h] [\-t] [\-x] [\-p PID]
+.SH DESCRIPTION
+This tool traces active TCP IPv4 connections (eg, via a connect() syscall;
+accept() are passive connections). This can be useful for general
+troubleshooting to see what connections are initiated by the local server.
+
+This works by tracing the kernel tcp_v4_connect() function using dynamic
+tracing, and will need updating to match any changes to this function.
+
+Since this uses BPF, only the root user can use this tool.
+.SH REQUIREMENTS
+CONFIG_BPF and bcc.
+.SH OPTIONS
+.TP
+\-h
+Print usage message.
+.TP
+\-t
+Include a timestamp column.
+.TP
+\-p PID
+Trace this process ID only (filtered in-kernel).
+.SH EXAMPLES
+.TP
+Trace all active TCP IPv4 connections:
+#
+.B tcpv4connect
+.TP
+Trace all TCP IPv4 connects, and include timestamps:
+#
+.B tcpv4connect \-t
+.TP
+Trace PID 181 only:
+#
+.B tcpv4connect \-p 181
+.SH FIELDS
+.TP
+TIME(s)
+Time of the call, in seconds.
+.TP
+PID
+Process ID
+.TP
+COMM
+Process name
+.TP
+SADDR
+IPv4 source address, as a dotted quad
+.TP
+DADDR
+IPv4 destination address, as a dotted quad
+.TP
+DPORT
+Destination port
+.SH OVERHEAD
+This traces the kernel tcp_v4_connect function and prints output for each event.
+As the rate of this is generally expected to be low (< 1000/s), the overhead is
+also expected to be negligible. If you have an application that is calling a high
+rate of connects()s, such as a proxy server, then test and understand this
+overhead before use.
+.SH SOURCE
+This is from bcc.
+.IP
+https://github.com/iovisor/bcc
+.PP
+Also look in the bcc distribution for a companion _examples.txt file containing
+example usage, output, and commentary for this tool.
+.SH OS
+Linux
+.SH STABILITY
+Unstable - in development.
+.SH AUTHOR
+Brendan Gregg
+.SH SEE ALSO
+funccount(8), tcpdump(8)

tools/tcpv4connect

+#!/usr/bin/python
+#
+# tcpv4connect	Trace TCP IPv4 connect()s.
+#		For Linux, uses BCC, eBPF. Embedded C.
+#
+# USAGE: tcpv4connect [-h] [-t] [-p PID]
+#
+# Copyright (c) 2015 Brendan Gregg.
+# Licensed under the Apache License, Version 2.0 (the "License")
+#
+# 25-Sep-2015	Brendan Gregg	Created this.
+
+from __future__ import print_function
+from bcc import BPF
+import argparse
+
+# arguments
+examples = """examples:
+    ./tcpv4connect           # trace all open() syscalls
+    ./tcpv4connect -t        # include timestamps
+    ./tcpv4connect -p 181    # only trace PID 181
+"""
+parser = argparse.ArgumentParser(
+	description="Trace TCP IPv4 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")
+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 *);
+
+int kprobe__tcp_v4_connect(struct pt_regs *ctx, struct sock *sk)
+{
+	u32 pid = bpf_get_current_pid_tgid();
+	FILTER
+
+	// 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 = ctx->ax;
+	u32 pid = bpf_get_current_pid_tgid();
+
+	struct sock **skpp;
+	skpp = currsock.lookup(&pid);
+	if (skpp == 0) {
+		return 0;	// missed entry
+	}
+
+	// pull in details
+	struct sock *skp = *skpp;
+	u32 saddr = 0, daddr = 0;
+	u16 dport = 0;
+	bpf_probe_read(&saddr, sizeof(saddr), &skp->__sk_common.skc_rcv_saddr);
+	bpf_probe_read(&daddr, sizeof(daddr), &skp->__sk_common.skc_daddr);
+	bpf_probe_read(&dport, sizeof(dport), &skp->__sk_common.skc_dport);
+
+	// output
+	bpf_trace_printk("%x %x %d\\n", saddr, daddr, ntohs(dport));
+
+	currsock.delete(&pid);
+
+	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 %-16s %-16s %-4s" % ("PID", "COMM", "SADDR", "DADDR",
+    "DPORT"))
+
+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()
+	(saddr_hs, daddr_hs, dport_s) = msg.split(" ")
+
+	if args.timestamp:
+		if start_ts == 0:
+			start_ts = ts
+		print("%-9.3f" % (ts - start_ts), end="")
+	print("%-6d %-12.12s %-16s %-16s %-4s" % (pid, task,
+	    inet_ntoa(int(saddr_hs, 16)),
+	    inet_ntoa(int(daddr_hs, 16)),
+	    dport_s))

tools/tcpv4connect_example.txt

+Demonstrations of tcpv4connect, the Linux eBPF/bcc version.
+
+
+This tool traces the kernel function performing active TCP IPv4 connections
+(eg, via a connect() syscall; accept() are passive connections). Some example
+output (IP addresses changed to protect the innocent):
+
+# ./tcpv4connect 
+PID    COMM         SADDR            DADDR            DPORT
+1479   telnet       127.0.0.1        127.0.0.1        23  
+1469   curl         10.201.219.236   54.245.105.25    80  
+1469   curl         10.201.219.236   54.67.101.145    80  
+
+This output shows three connections, one from a "telnet" process and two from
+"curl". The output details shows the source address, destination address,
+and destination port. This traces attempted connections: these may have failed.
+
+The overhead of this tool should be negligible, since it is only tracing the
+kernel function performing a connect. It is not tracing every packet and then
+filtering.
+
+
+The -t option prints a timestamp column:
+
+# ./tcpv4connect -t
+TIME(s)  PID    COMM         SADDR            DADDR            DPORT
+31.871   2482   local_agent  10.103.219.236   10.251.148.38    7001
+31.874   2482   local_agent  10.103.219.236   10.101.3.132     7001
+31.878   2482   local_agent  10.103.219.236   10.171.133.98    7101
+90.917   2482   local_agent  10.103.219.236   10.251.148.38    7001
+90.928   2482   local_agent  10.103.219.236   10.102.64.230    7001
+90.938   2482   local_agent  10.103.219.236   10.115.167.169   7101
+
+The output shows some periodic connections (or attempts) from a "local_agent"
+process to various other addresses. A few connections occur every minute.
+
+
+USAGE message:
+
+# ./tcpv4connect -h
+usage: tcpv4connect [-h] [-t] [-p PID]
+
+Trace TCP IPv4 connects
+
+optional arguments:
+  -h, --help         show this help message and exit
+  -t, --timestamp    include timestamp on output
+  -p PID, --pid PID  trace this PID only
+
+examples:
+    ./tcpv4connect           # trace all open() syscalls
+    ./tcpv4connect -t        # include timestamps
+    ./tcpv4connect -p 181    # only trace PID 181