什么原因导致 Linux 邻居表确认计数器被重置

2024-5-30 • tag-icon

鉴于同一广播域中的三个 Linux 主机，sender不断 ping 绑定到的 IP receiver1。

当将 IP 地址从移动receiver1到时receiver2，ARP/邻居缓存需要很长时间才能失效sender。

在监控邻居缓存统计数据时，confirmation尽管没有收到来自邻居条目的入站流量，但计数器仍会以不规则的方式重置。

一个例子：

sender: 172.22.5.79 / 00:1b:21:cd:a3:11
receiver1: b0:83:fe:da:7e:95
receiver2: b0:83:fe:da:83:ab
moving ip: 172.22.15.188

IP 在 10:33:06 和 10:33:07 之间移动。

发送方的 tcpdump：

10:33:02.967762 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 31, length 64
10:33:02.968855 b0:83:fe:da:7e:95 > 00:1b:21:cd:a3:11, ethertype IPv4 (0x0800), length 98: 172.22.15.188 > 172.22.5.79: ICMP echo reply, id 20133, seq 31, length 64
10:33:03.968901 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 32, length 64
10:33:03.980530 b0:83:fe:da:7e:95 > 00:1b:21:cd:a3:11, ethertype IPv4 (0x0800), length 98: 172.22.15.188 > 172.22.5.79: ICMP echo reply, id 20133, seq 32, length 64
10:33:04.970580 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 33, length 64
10:33:04.970714 b0:83:fe:da:7e:95 > 00:1b:21:cd:a3:11, ethertype IPv4 (0x0800), length 98: 172.22.15.188 > 172.22.5.79: ICMP echo reply, id 20133, seq 33, length 64
10:33:05.969581 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 34, length 64
10:33:05.969748 b0:83:fe:da:7e:95 > 00:1b:21:cd:a3:11, ethertype IPv4 (0x0800), length 98: 172.22.15.188 > 172.22.5.79: ICMP echo reply, id 20133, seq 34, length 64
10:33:06.968585 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 35, length 64
10:33:06.968685 b0:83:fe:da:7e:95 > 00:1b:21:cd:a3:11, ethertype IPv4 (0x0800), length 98: 172.22.15.188 > 172.22.5.79: ICMP echo reply, id 20133, seq 35, length 64
10:33:07.967738 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 36, length 64
10:33:08.967756 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 37, length 64
10:33:09.967761 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 38, length 64
10:33:10.967752 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 39, length 64
10:33:11.967769 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 40, length 64
10:33:12.967750 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 41, length 64
10:33:13.967749 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 42, length 64
10:33:14.967760 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 43, length 64
10:33:15.967735 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 44, length 64
10:33:16.967745 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 45, length 64
10:33:17.967756 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 46, length 64
10:33:18.967784 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 47, length 64
10:33:19.967762 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 48, length 64
10:33:20.967775 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 49, length 64
10:33:21.967748 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 50, length 64
10:33:22.967737 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 51, length 64
10:33:23.967743 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 52, length 64
10:33:24.967773 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 53, length 64
10:33:25.967757 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 54, length 64
10:33:26.967760 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 55, length 64
10:33:27.967755 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 56, length 64
10:33:28.971748 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 57, length 64
10:33:29.971744 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 58, length 64
10:33:30.971757 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 59, length 64
10:33:31.971758 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 60, length 64
10:33:32.971782 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 61, length 64
10:33:33.971793 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 62, length 64
10:33:34.971790 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 63, length 64
10:33:35.971779 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 64, length 64
10:33:36.971765 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 65, length 64
10:33:37.971769 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 66, length 64
10:33:38.971756 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 67, length 64
10:33:39.971734 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 68, length 64
10:33:40.971752 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 69, length 64
10:33:41.971749 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 70, length 64
10:33:42.971755 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 71, length 64
10:33:43.971766 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 72, length 64
10:33:44.971753 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 73, length 64
10:33:45.971757 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 74, length 64
10:33:46.971794 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 75, length 64
10:33:47.971750 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 76, length 64
10:33:48.971765 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 77, length 64
10:33:49.971744 00:1b:21:cd:a3:11 > b0:83:fe:da:7e:95, ethertype IPv4 (0x0800), length 98: 172.22.5.79 > 172.22.15.188: ICMP echo request, id 20133, seq 78, length 64

同一时间范围内发送方邻居表的内容：

Thu Jul 16 10:32:56 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 464/0/464 probes 4 REACHABLE
Thu Jul 16 10:32:57 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 465/0/465 probes 4 REACHABLE
Thu Jul 16 10:32:58 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 466/0/466 probes 4 REACHABLE
Thu Jul 16 10:32:59 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 467/0/467 probes 4 REACHABLE
Thu Jul 16 10:33:00 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 468/0/468 probes 4 REACHABLE
Thu Jul 16 10:33:01 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 469/0/469 probes 4 REACHABLE
Thu Jul 16 10:33:02 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 470/0/470 probes 4 REACHABLE
Thu Jul 16 10:33:03 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 471/0/471 probes 4 REACHABLE
Thu Jul 16 10:33:04 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 472/0/472 probes 4 REACHABLE
Thu Jul 16 10:33:05 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 473/0/473 probes 4 REACHABLE
Thu Jul 16 10:33:06 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 474/0/474 probes 4 REACHABLE
Thu Jul 16 10:33:07 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 475/0/475 probes 4 REACHABLE
Thu Jul 16 10:33:08 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 476/0/476 probes 4 REACHABLE
Thu Jul 16 10:33:09 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 477/1/477 probes 4 REACHABLE
Thu Jul 16 10:33:10 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 478/2/478 probes 4 REACHABLE
Thu Jul 16 10:33:11 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 479/3/479 probes 4 REACHABLE
Thu Jul 16 10:33:12 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 480/0/480 probes 4 REACHABLE
Thu Jul 16 10:33:13 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 481/1/481 probes 4 REACHABLE
Thu Jul 16 10:33:14 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 482/2/482 probes 4 REACHABLE
Thu Jul 16 10:33:15 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 483/3/483 probes 4 REACHABLE
Thu Jul 16 10:33:16 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 484/4/484 probes 4 REACHABLE
Thu Jul 16 10:33:17 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 485/5/485 probes 4 REACHABLE
Thu Jul 16 10:33:18 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 486/6/486 probes 4 REACHABLE
Thu Jul 16 10:33:19 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 488/0/488 probes 4 REACHABLE
Thu Jul 16 10:33:20 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 489/0/489 probes 4 REACHABLE
Thu Jul 16 10:33:21 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 490/1/490 probes 4 REACHABLE
Thu Jul 16 10:33:22 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 491/2/491 probes 4 REACHABLE
Thu Jul 16 10:33:23 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 492/3/492 probes 4 REACHABLE
Thu Jul 16 10:33:24 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 493/4/493 probes 4 REACHABLE
Thu Jul 16 10:33:25 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 494/5/494 probes 4 REACHABLE
Thu Jul 16 10:33:26 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 495/6/495 probes 4 REACHABLE
Thu Jul 16 10:33:27 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 496/7/496 probes 4 REACHABLE
Thu Jul 16 10:33:28 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 497/8/497 probes 4 REACHABLE
Thu Jul 16 10:33:29 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 498/9/498 probes 4 REACHABLE
Thu Jul 16 10:33:30 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 499/10/499 probes 4 REACHABLE
Thu Jul 16 10:33:31 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 500/11/500 probes 4 REACHABLE
Thu Jul 16 10:33:32 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 501/12/501 probes 4 REACHABLE
Thu Jul 16 10:33:33 UTC 2015  172.22.15.188 dev eth1 lladdr b0:83:fe:da:7e:95 ref 1 used 502/13/502 probes 4 REACHABLE

网络流量的完整转储表明，除了来自发送方的出站 ICMP 数据包外，节点之间没有进一步的通信。

当计时器最终到期或在receiver2IP 移动后发送免费 ARP 请求后，这种情况会在 5 到 30 分钟之间随机地自行纠正。

进一步阅读

没有提供关于这里发生的事情的见解。

为了澄清起见，我预计，在默认设置下，ARP 条目最坏会在 50 秒后指向新的 MAC 地址。

根据arp(7)各自的可调参数

base_reachable_time：[..an..] 条目被认为至少在 base_reachable_time/2 和 3*base_reachable_time/2 之间的随机值内有效。默认值：30 秒
delay_first_probe_time：在确定邻居已过时后，第一次探测之前的延迟。默认值：5 秒

3 * 30 / 2 + 5 = 50

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