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#! /usr/bin/python3
# @lint-avoid-python-3-compatibility-imports
#
# tcpretrans Trace or count TCP retransmits and TLPs.
# For Linux, uses BCC, eBPF. Embedded C.
#
# USAGE: tcpretrans [-c] [-h] [-l] [-4 | -6]
#
# This uses dynamic tracing of kernel functions, and will need to be updated
# to match kernel changes.
#
# Copyright 2016 Netflix, Inc.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 14-Feb-2016 Brendan Gregg Created this.
# 03-Nov-2017 Matthias Tafelmeier Extended this.
from __future__ import print_function
from bcc import BPF
import argparse
from time import strftime
from socket import inet_ntop, AF_INET, AF_INET6
from struct import pack
from time import sleep
# arguments
examples = """examples:
./tcpretrans # trace TCP retransmits
./tcpretrans -l # include TLP attempts
./tcpretrans -4 # trace IPv4 family only
./tcpretrans -6 # trace IPv6 family only
"""
parser = argparse.ArgumentParser(
description="Trace TCP retransmits",
formatter_class=argparse.RawDescriptionHelpFormatter,
epilog=examples)
parser.add_argument("-s", "--sequence", action="store_true",
help="display TCP sequence numbers")
parser.add_argument("-l", "--lossprobe", action="store_true",
help="include tail loss probe attempts")
parser.add_argument("-c", "--count", action="store_true",
help="count occurred retransmits per flow")
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("--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 <net/tcp.h>
#include <bcc/proto.h>
#define RETRANSMIT 1
#define TLP 2
// separate data structs for ipv4 and ipv6
struct ipv4_data_t {
u32 pid;
u64 ip;
u32 seq;
u32 saddr;
u32 daddr;
u16 lport;
u16 dport;
u64 state;
u64 type;
};
BPF_PERF_OUTPUT(ipv4_events);
struct ipv6_data_t {
u32 pid;
u32 seq;
u64 ip;
unsigned __int128 saddr;
unsigned __int128 daddr;
u16 lport;
u16 dport;
u64 state;
u64 type;
};
BPF_PERF_OUTPUT(ipv6_events);
// separate flow keys per address family
struct ipv4_flow_key_t {
u32 saddr;
u32 daddr;
u16 lport;
u16 dport;
};
BPF_HASH(ipv4_count, struct ipv4_flow_key_t);
struct ipv6_flow_key_t {
unsigned __int128 saddr;
unsigned __int128 daddr;
u16 lport;
u16 dport;
};
BPF_HASH(ipv6_count, struct ipv6_flow_key_t);
"""
bpf_text_kprobe = """
static int trace_event(struct pt_regs *ctx, struct sock *skp, struct sk_buff *skb, int type)
{
struct tcp_skb_cb *tcb;
u32 seq;
if (skp == NULL)
return 0;
u32 pid = bpf_get_current_pid_tgid() >> 32;
// pull in details
u16 family = skp->__sk_common.skc_family;
u16 lport = skp->__sk_common.skc_num;
u16 dport = skp->__sk_common.skc_dport;
char state = skp->__sk_common.skc_state;
seq = 0;
if (skb) {
/* macro TCP_SKB_CB from net/tcp.h */
tcb = ((struct tcp_skb_cb *)&((skb)->cb[0]));
seq = tcb->seq;
}
FILTER_FAMILY
if (family == AF_INET) {
IPV4_INIT
IPV4_CORE
} else if (family == AF_INET6) {
IPV6_INIT
IPV6_CORE
}
// else drop
return 0;
}
"""
bpf_text_kprobe_retransmit = """
int trace_retransmit(struct pt_regs *ctx, struct sock *sk, struct sk_buff *skb)
{
trace_event(ctx, sk, skb, RETRANSMIT);
return 0;
}
"""
bpf_text_kprobe_tlp = """
int trace_tlp(struct pt_regs *ctx, struct sock *sk)
{
trace_event(ctx, sk, NULL, TLP);
return 0;
}
"""
bpf_text_tracepoint = """
TRACEPOINT_PROBE(tcp, tcp_retransmit_skb)
{
struct tcp_skb_cb *tcb;
u32 seq;
u32 pid = bpf_get_current_pid_tgid() >> 32;
const struct sock *skp = (const struct sock *)args->skaddr;
const struct sk_buff *skb = (const struct sk_buff *)args->skbaddr;
u16 lport = args->sport;
u16 dport = args->dport;
char state = skp->__sk_common.skc_state;
u16 family = skp->__sk_common.skc_family;
seq = 0;
if (skb) {
/* macro TCP_SKB_CB from net/tcp.h */
tcb = ((struct tcp_skb_cb *)&((skb)->cb[0]));
seq = tcb->seq;
}
FILTER_FAMILY
if (family == AF_INET) {
IPV4_CODE
} else if (family == AF_INET6) {
IPV6_CODE
}
return 0;
}
"""
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;
// lport is host order
flow_key.lport = lport;
flow_key.dport = ntohs(dport);""",
'trace' :
"""
struct ipv4_data_t data4 = {};
data4.pid = pid;
data4.ip = 4;
data4.seq = seq;
data4.type = type;
data4.saddr = skp->__sk_common.skc_rcv_saddr;
data4.daddr = skp->__sk_common.skc_daddr;
// lport is host order
data4.lport = lport;
data4.dport = ntohs(dport);
data4.state = state; """
},
'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);
// lport is host order
flow_key.lport = lport;
flow_key.dport = ntohs(dport);""",
'trace' : """
struct ipv6_data_t data6 = {};
data6.pid = pid;
data6.ip = 6;
data6.seq = seq;
data6.type = type;
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);
// lport is host order
data6.lport = lport;
data6.dport = ntohs(dport);
data6.state = state;"""
}
}
struct_init_tracepoint = { 'ipv4':
{ 'count' : """
struct ipv4_flow_key_t flow_key = {};
__builtin_memcpy(&flow_key.saddr, args->saddr, sizeof(flow_key.saddr));
__builtin_memcpy(&flow_key.daddr, args->daddr, sizeof(flow_key.daddr));
flow_key.lport = lport;
flow_key.dport = dport;
ipv4_count.increment(flow_key);
""",
'trace' : """
struct ipv4_data_t data4 = {};
data4.pid = pid;
data4.lport = lport;
data4.dport = dport;
data4.type = RETRANSMIT;
data4.ip = 4;
data4.seq = seq;
data4.state = state;
__builtin_memcpy(&data4.saddr, args->saddr, sizeof(data4.saddr));
__builtin_memcpy(&data4.daddr, args->daddr, sizeof(data4.daddr));
ipv4_events.perf_submit(args, &data4, sizeof(data4));
"""
},
'ipv6':
{ 'count' : """
struct ipv6_flow_key_t flow_key = {};
__builtin_memcpy(&flow_key.saddr, args->saddr_v6, sizeof(flow_key.saddr));
__builtin_memcpy(&flow_key.daddr, args->daddr_v6, sizeof(flow_key.daddr));
flow_key.lport = lport;
flow_key.dport = dport;
ipv6_count.increment(flow_key);
""",
'trace' : """
struct ipv6_data_t data6 = {};
data6.pid = pid;
data6.lport = lport;
data6.dport = dport;
data6.type = RETRANSMIT;
data6.ip = 6;
data6.seq = seq;
data6.state = state;
__builtin_memcpy(&data6.saddr, args->saddr_v6, sizeof(data6.saddr));
__builtin_memcpy(&data6.daddr, args->daddr_v6, sizeof(data6.daddr));
ipv6_events.perf_submit(args, &data6, sizeof(data6));
"""
}
}
count_core_base = """
COUNT_STRUCT.increment(flow_key);
"""
if BPF.tracepoint_exists("tcp", "tcp_retransmit_skb"):
if args.count:
bpf_text_tracepoint = bpf_text_tracepoint.replace("IPV4_CODE", struct_init_tracepoint['ipv4']['count'])
bpf_text_tracepoint = bpf_text_tracepoint.replace("IPV6_CODE", struct_init_tracepoint['ipv6']['count'])
else:
bpf_text_tracepoint = bpf_text_tracepoint.replace("IPV4_CODE", struct_init_tracepoint['ipv4']['trace'])
bpf_text_tracepoint = bpf_text_tracepoint.replace("IPV6_CODE", struct_init_tracepoint['ipv6']['trace'])
bpf_text += bpf_text_tracepoint
if args.lossprobe or not BPF.tracepoint_exists("tcp", "tcp_retransmit_skb"):
bpf_text += bpf_text_kprobe
if args.count:
bpf_text = bpf_text.replace("IPV4_INIT", struct_init['ipv4']['count'])
bpf_text = bpf_text.replace("IPV6_INIT", struct_init['ipv6']['count'])
bpf_text = bpf_text.replace("IPV4_CORE", count_core_base.replace("COUNT_STRUCT", 'ipv4_count'))
bpf_text = bpf_text.replace("IPV6_CORE", count_core_base.replace("COUNT_STRUCT", 'ipv6_count'))
else:
bpf_text = bpf_text.replace("IPV4_INIT", struct_init['ipv4']['trace'])
bpf_text = bpf_text.replace("IPV6_INIT", struct_init['ipv6']['trace'])
bpf_text = bpf_text.replace("IPV4_CORE", "ipv4_events.perf_submit(ctx, &data4, sizeof(data4));")
bpf_text = bpf_text.replace("IPV6_CORE", "ipv6_events.perf_submit(ctx, &data6, sizeof(data6));")
if args.lossprobe:
bpf_text += bpf_text_kprobe_tlp
if not BPF.tracepoint_exists("tcp", "tcp_retransmit_skb"):
bpf_text += bpf_text_kprobe_retransmit
if args.ipv4:
bpf_text = bpf_text.replace('FILTER_FAMILY',
'if (family != AF_INET) { return 0; }')
elif args.ipv6:
bpf_text = bpf_text.replace('FILTER_FAMILY',
'if (family != AF_INET6) { return 0; }')
else:
bpf_text = bpf_text.replace('FILTER_FAMILY', '')
if debug or args.ebpf:
print(bpf_text)
if args.ebpf:
exit()
# from bpf_text:
type = {}
type[1] = 'R'
type[2] = 'L'
# from include/net/tcp_states.h:
tcpstate = {}
tcpstate[1] = 'ESTABLISHED'
tcpstate[2] = 'SYN_SENT'
tcpstate[3] = 'SYN_RECV'
tcpstate[4] = 'FIN_WAIT1'
tcpstate[5] = 'FIN_WAIT2'
tcpstate[6] = 'TIME_WAIT'
tcpstate[7] = 'CLOSE'
tcpstate[8] = 'CLOSE_WAIT'
tcpstate[9] = 'LAST_ACK'
tcpstate[10] = 'LISTEN'
tcpstate[11] = 'CLOSING'
tcpstate[12] = 'NEW_SYN_RECV'
# process event
def print_ipv4_event(cpu, data, size):
event = b["ipv4_events"].event(data)
print("%-8s %-7d %-2d %-20s %1s> %-20s" % (
strftime("%H:%M:%S"), event.pid, event.ip,
"%s:%d" % (inet_ntop(AF_INET, pack('I', event.saddr)), event.lport),
type[event.type],
"%s:%s" % (inet_ntop(AF_INET, pack('I', event.daddr)), event.dport)),
end='')
if args.sequence:
print(" %-12s %s" % (tcpstate[event.state], event.seq))
else:
print(" %s" % (tcpstate[event.state]))
def print_ipv6_event(cpu, data, size):
event = b["ipv6_events"].event(data)
print("%-8s %-7d %-2d %-20s %1s> %-20s" % (
strftime("%H:%M:%S"), event.pid, event.ip,
"%s:%d" % (inet_ntop(AF_INET6, event.saddr), event.lport),
type[event.type],
"%s:%d" % (inet_ntop(AF_INET6, event.daddr), event.dport)),
end='')
if args.sequence:
print(" %-12s %s" % (tcpstate[event.state], event.seq))
else:
print(" %s" % (tcpstate[event.state]))
def depict_cnt(counts_tab, l3prot='ipv4'):
for k, v in sorted(counts_tab.items(), key=lambda counts: counts[1].value):
depict_key = ""
ep_fmt = "[%s]#%d"
if l3prot == 'ipv4':
depict_key = "%-20s <-> %-20s" % (ep_fmt % (inet_ntop(AF_INET, pack('I', k.saddr)), k.lport),
ep_fmt % (inet_ntop(AF_INET, pack('I', k.daddr)), k.dport))
else:
depict_key = "%-20s <-> %-20s" % (ep_fmt % (inet_ntop(AF_INET6, k.saddr), k.lport),
ep_fmt % (inet_ntop(AF_INET6, k.daddr), k.dport))
print ("%s %10d" % (depict_key, v.value))
# initialize BPF
b = BPF(text=bpf_text)
if not BPF.tracepoint_exists("tcp", "tcp_retransmit_skb"):
b.attach_kprobe(event="tcp_retransmit_skb", fn_name="trace_retransmit")
if args.lossprobe:
b.attach_kprobe(event="tcp_send_loss_probe", fn_name="trace_tlp")
print("Tracing retransmits ... Hit Ctrl-C to end")
if args.count:
try:
while 1:
sleep(99999999)
except BaseException:
pass
# header
print("\n%-25s %-25s %-10s" % (
"LADDR:LPORT", "RADDR:RPORT", "RETRANSMITS"))
depict_cnt(b.get_table("ipv4_count"))
depict_cnt(b.get_table("ipv6_count"), l3prot='ipv6')
# read events
else:
# header
print("%-8s %-7s %-2s %-20s %1s> %-20s" % ("TIME", "PID", "IP",
"LADDR:LPORT", "T", "RADDR:RPORT"), end='')
if args.sequence:
print(" %-12s %-10s" % ("STATE", "SEQ"))
else:
print(" %-4s" % ("STATE"))
b["ipv4_events"].open_perf_buffer(print_ipv4_event)
b["ipv6_events"].open_perf_buffer(print_ipv6_event)
while 1:
try:
b.perf_buffer_poll()
except KeyboardInterrupt:
exit()
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