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#! /usr/bin/python3
# @lint-avoid-python-3-compatibility-imports
#
# sofdsnoop traces file descriptors passed via socket
# For Linux, uses BCC, eBPF. Embedded C.
#
# USAGE: sofdsnoop
#
# Copyright (c) 2018 Jiri Olsa.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 30-Jul-2018 Jiri Olsa Created this.
from __future__ import print_function
from bcc import ArgString, BPF
import os
import argparse
from datetime import datetime, timedelta
# arguments
examples = """examples:
./sofdsnoop # trace passed file descriptors
./sofdsnoop -T # include timestamps
./sofdsnoop -p 181 # only trace PID 181
./sofdsnoop -t 123 # only trace TID 123
./sofdsnoop -d 10 # trace for 10 seconds only
./sofdsnoop -n main # only print process names containing "main"
"""
parser = argparse.ArgumentParser(
description="Trace file descriptors passed via socket",
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("-t", "--tid",
help="trace this TID only")
parser.add_argument("-n", "--name",
type=ArgString,
help="only print process names containing this name")
parser.add_argument("-d", "--duration",
help="total duration of trace in seconds")
args = parser.parse_args()
debug = 0
ACTION_SEND=0
ACTION_RECV=1
MAX_FD=10
if args.duration:
args.duration = timedelta(seconds=int(args.duration))
# define BPF program
bpf_text = """
#include <uapi/linux/ptrace.h>
#include <uapi/linux/limits.h>
#include <linux/sched.h>
#include <linux/socket.h>
#include <net/sock.h>
#define MAX_FD 10
#define ACTION_SEND 0
#define ACTION_RECV 1
struct val_t {
u64 id;
u64 ts;
int action;
int sock_fd;
int fd_cnt;
int fd[MAX_FD];
char comm[TASK_COMM_LEN];
};
BPF_HASH(detach_ptr, u64, struct cmsghdr *);
BPF_HASH(sock_fd, u64, int);
BPF_PERF_OUTPUT(events);
static void set_fd(int fd)
{
u64 id = bpf_get_current_pid_tgid();
sock_fd.update(&id, &fd);
}
static int get_fd(void)
{
u64 id = bpf_get_current_pid_tgid();
int *fd;
fd = sock_fd.lookup(&id);
return fd ? *fd : -1;
}
static void put_fd(void)
{
u64 id = bpf_get_current_pid_tgid();
sock_fd.delete(&id);
}
static int sent_1(struct pt_regs *ctx, struct val_t *val, int num, void *data)
{
val->fd_cnt = min(num, MAX_FD);
if (bpf_probe_read_kernel(&val->fd[0], MAX_FD * sizeof(int), data))
return -1;
events.perf_submit(ctx, val, sizeof(*val));
return 0;
}
#define SEND_1 \
if (sent_1(ctx, &val, num, (void *) data)) \
return 0; \
\
num -= MAX_FD; \
if (num < 0) \
return 0; \
\
data += MAX_FD;
#define SEND_2 SEND_1 SEND_1
#define SEND_4 SEND_2 SEND_2
#define SEND_8 SEND_4 SEND_4
#define SEND_260 SEND_8 SEND_8 SEND_8 SEND_2
static int send(struct pt_regs *ctx, struct cmsghdr *cmsg, int action)
{
struct val_t val = { 0 };
int *data, num, fd;
u64 tsp = bpf_ktime_get_ns();
data = (void *) ((char *) cmsg + sizeof(struct cmsghdr));
num = (cmsg->cmsg_len - sizeof(struct cmsghdr)) / sizeof(int);
val.id = bpf_get_current_pid_tgid();
val.action = action;
val.sock_fd = get_fd();
val.ts = tsp / 1000;
if (bpf_get_current_comm(&val.comm, sizeof(val.comm)) != 0)
return 0;
SEND_260
return 0;
}
static bool allow_pid(u64 id)
{
u32 pid = id >> 32; // PID is higher part
u32 tid = id; // Cast and get the lower part
FILTER
return 1;
}
int trace_scm_send_entry(struct pt_regs *ctx, struct socket *sock, struct msghdr *hdr)
{
struct cmsghdr *cmsg = NULL;
if (!allow_pid(bpf_get_current_pid_tgid()))
return 0;
if (hdr->msg_controllen >= sizeof(struct cmsghdr))
cmsg = hdr->msg_control;
if (!cmsg || (cmsg->cmsg_type != SCM_RIGHTS))
return 0;
return send(ctx, cmsg, ACTION_SEND);
};
int trace_scm_detach_fds_entry(struct pt_regs *ctx, struct msghdr *hdr)
{
struct cmsghdr *cmsg = NULL;
u64 id = bpf_get_current_pid_tgid();
if (!allow_pid(id))
return 0;
if (hdr->msg_controllen >= sizeof(struct cmsghdr))
cmsg = hdr->msg_control;
if (!cmsg)
return 0;
detach_ptr.update(&id, &cmsg);
return 0;
};
int trace_scm_detach_fds_return(struct pt_regs *ctx)
{
struct cmsghdr **cmsgp;
u64 id = bpf_get_current_pid_tgid();
if (!allow_pid(id))
return 0;
cmsgp = detach_ptr.lookup(&id);
if (!cmsgp)
return 0;
return send(ctx, *cmsgp, ACTION_RECV);
}
int syscall__sendmsg(struct pt_regs *ctx, u64 fd, u64 msg, u64 flags)
{
struct pt_regs p;
if (!allow_pid(bpf_get_current_pid_tgid()))
return 0;
set_fd(fd);
return 0;
}
int trace_sendmsg_return(struct pt_regs *ctx)
{
if (!allow_pid(bpf_get_current_pid_tgid()))
return 0;
put_fd();
return 0;
}
int syscall__recvmsg(struct pt_regs *ctx, u64 fd, u64 msg, u64 flags)
{
struct pt_regs p;
if (!allow_pid(bpf_get_current_pid_tgid()))
return 0;
fd = fd;
set_fd(fd);
return 0;
}
int trace_recvmsg_return(struct pt_regs *ctx)
{
if (!allow_pid(bpf_get_current_pid_tgid()))
return 0;
put_fd();
return 0;
}
"""
if args.tid: # TID trumps PID
bpf_text = bpf_text.replace('FILTER',
'if (tid != %s) { return 0; }' % args.tid)
elif args.pid:
bpf_text = bpf_text.replace('FILTER',
'if (pid != %s) { return 0; }' % args.pid)
else:
bpf_text = bpf_text.replace('FILTER', '')
# initialize BPF
b = BPF(text=bpf_text)
syscall_fnname = b.get_syscall_fnname("sendmsg")
if BPF.ksymname(syscall_fnname) != -1:
b.attach_kprobe(event=syscall_fnname, fn_name="syscall__sendmsg")
b.attach_kretprobe(event=syscall_fnname, fn_name="trace_sendmsg_return")
syscall_fnname = b.get_syscall_fnname("recvmsg")
if BPF.ksymname(syscall_fnname) != -1:
b.attach_kprobe(event=syscall_fnname, fn_name="syscall__recvmsg")
b.attach_kretprobe(event=syscall_fnname, fn_name="trace_recvmsg_return")
b.attach_kprobe(event="__scm_send", fn_name="trace_scm_send_entry")
b.attach_kprobe(event="scm_detach_fds", fn_name="trace_scm_detach_fds_entry")
b.attach_kretprobe(event="scm_detach_fds", fn_name="trace_scm_detach_fds_return")
initial_ts = 0
# header
if args.timestamp:
print("%-14s" % ("TIME(s)"), end="")
print("%-6s %-6s %-16s %-25s %-5s %s" %
("ACTION", "TID", "COMM", "SOCKET", "FD", "NAME"))
def get_file(pid, fd):
proc = "/proc/%d/fd/%d" % (pid, fd)
try:
return os.readlink(proc)
except OSError as err:
return "N/A"
# process event
def print_event(cpu, data, size):
event = b["events"].event(data)
tid = event.id & 0xffffffff;
cnt = min(MAX_FD, event.fd_cnt);
if args.name and bytes(args.name) not in event.comm:
return
for i in range(0, cnt):
global initial_ts
if not initial_ts:
initial_ts = event.ts
if args.timestamp:
delta = event.ts - initial_ts
print("%-14.9f" % (float(delta) / 1000000), end="")
print("%-6s %-6d %-16s " %
("SEND" if event.action == ACTION_SEND else "RECV",
tid, event.comm.decode()), end = '')
sock = "%d:%s" % (event.sock_fd, get_file(tid, event.sock_fd))
print("%-25s " % sock, end = '')
fd = event.fd[i]
fd_file = get_file(tid, fd) if event.action == ACTION_SEND else ""
print("%-5d %s" % (fd, fd_file))
# loop with callback to print_event
b["events"].open_perf_buffer(print_event, page_cnt=64)
start_time = datetime.now()
while not args.duration or datetime.now() - start_time < args.duration:
try:
b.perf_buffer_poll(timeout=1000)
except KeyboardInterrupt:
exit()
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