IPv6 Router Advertisement Floods (by quqi99)
作者：张华 发表于：2016-06-23
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( http://blog.csdn.net/quqi99 )
今天，遇到一个很诡异的问题，当ssh连接远程虚机做实验时，突然连接断开了。最后查出的原因如下：有一个脚本执行一次会给虚机增加一块网卡并加到br-ex里去，当再执行一次br-ex里会添加第二块网卡，会造成IPv6 router advertisement floods，然后虚机会变得奇慢无比，然后ssh连接断开。实验结果如下：
1, 当往br-ex里添加第一块网卡，且radvd关闭时：
23:50:50.306032 IP 192.168.102.1.50264 > 192.168.102.100.ssh: Flags [P.], seq 2234092183:2234092219, ack 99372432, win 342, options [nop,nop,TS val 51145217 ecr 33461], length 36 23:50:50.306542 IP 192.168.102.100.ssh > 192.168.102.1.50264: Flags [P.], seq 1:37, ack 36, win 312, options [nop,nop,TS val 39271 ecr 51145217], length 36 23:50:50.306556 IP 192.168.102.1.50264 > 192.168.102.100.ssh: Flags [.], ack 37, win 342, options [nop,nop,TS val 51145217 ecr 39271], length 0 23:50:50.362157 IP 192.168.102.1.50264 > 192.168.102.100.ssh: Flags [P.], seq 36:72, ack 37, win 342, options [nop,nop,TS val 51145231 ecr 39271], length 36 23:50:50.362490 IP 192.168.102.100.ssh > 192.168.102.1.50264: Flags [P.], seq 37:73, ack 72, win 312, options [nop,nop,TS val 39285 ecr 51145231], length 36 23:50:50.362506 IP 192.168.102.1.50264 > 192.168.102.100.ssh: Flags [.], ack 73, win 342, options [nop,nop,TS val 51145231 ecr 39285], length 0 23:50:50.493481 IP 192.168.102.1.50264 > 192.168.102.100.ssh: Flags [P.], seq 72:108, ack 73, win 342, options [nop,nop,TS val 51145264 ecr 39285], length 36 23:50:50.915926 IP 192.168.102.1.50264 > 192.168.102.100.ssh: Flags [P.], seq 216:252, ack 217, win 342, options [nop,nop,TS val 51145369 ecr 39393], length 36 23:50:50.916389 IP 192.168.102.100.ssh > 192.168.102.1.50264: Flags [P.], seq 217:253, ack 252, win 312, options [nop,nop,TS val 39424 ecr 51145369], length 36 23:50:50.916415 IP 192.168.102.1.50264 > 192.168.102.100.ssh: Flags [.], ack 253, win 342, options [nop,nop,TS val 51145369 ecr 39424], length 0 23:50:51.096128 IP 192.168.102.1.50264 > 192.168.102.100.ssh: Flags [P.], seq 252:288, ack 253, win 342, options [nop,nop,TS val 51145414 ecr 39424], length 36 23:50:51.096502 IP 192.168.102.100.ssh > 192.168.102.1.50264: Flags [P.], seq 253:289, ack 288, win 312, options [nop,nop,TS val 39469 ecr 51145414], length 36 23:50:51.096521 IP 192.168.102.1.50264 > 192.168.102.100.ssh: Flags [.], ack 289, win 342, options [nop,nop,TS val 51145414 ecr 39469], length 0 23:50:51.152884 IP 192.168.102.1.50264 > 192.168.102.100.ssh: Flags [P.], seq 288:324, ack 289, win 342, options [nop,nop,TS val 51145429 ecr 39469], length 36 23:50:51.153268 IP 192.168.102.100.ssh > 192.168.102.1.50264: Flags [P.], seq 289:325, ack 324, win 312, options [nop,nop,TS val 39483 ecr 51145429], length 36
2, 当往br-ex里添加第二块网卡，且radvd关闭时，ssh连接不会断开。
23:52:13.634073 IP6 fe80::5054:ff:fef1:6bf4 > ff02::16: HBH ICMP6, multicast listener report v2, 1 group record(s), length 28 23:52:13.634115 IP6 :: > ff02::16: HBH ICMP6, multicast listener report v2, 1 group record(s), length 28 23:52:13.634157 IP6 fe80::5054:ff:fef1:6bf4 > ff02::16: HBH ICMP6, multicast listener report v2, 1 group record(s), length 28 23:52:13.634199 IP6 fe80::5054:ff:fef1:6bf4 > ip6-allrouters: ICMP6, router solicitation, length 16 23:52:13.634256 IP6 fe80::5054:ff:fef1:6bf4 > ip6-allrouters: ICMP6, router solicitation, length 16 23:52:13.634308 IP6 :: > ff02::16: HBH ICMP6, multicast listener report v2, 1 group record(s), length 28 23:52:13.634367 IP6 fe80::5054:ff:fef1:6bf4 > ip6-allrouters: ICMP6, router solicitation, length 16 23:52:13.634417 IP6 :: > ff02::1:fff1:6bf4: ICMP6, neighbor solicitation, who has fe80::5054:ff:fef1:6bf4, length 24 23:52:13.634484 IP6 fe80::5054:ff:fef1:6bf4 > ff02::16: HBH ICMP6, multicast listener report v2, 1 group record(s), length 28 23:52:13.634529 IP6 :: > ff02::16: HBH ICMP6, multicast listener report v2, 1 group record(s), length 28 23:52:13.634608 IP6 fe80::5054:ff:fef1:6bf4 > ff02::16: HBH ICMP6, multicast listener report v2, 1 group record(s), length 28 23:52:13.634676 IP6 fe80::5054:ff:fef1:6bf4 > ip6-allrouters: ICMP6, router solicitation, length 16 23:52:13.634729 IP6 fe80::5054:ff:fef1:6bf4 > ip6-allrouters: ICMP6, router solicitation, length 16 23:52:13.634779 IP6 :: > ff02::16: HBH ICMP6, multicast listener report v2, 1 group record(s), length 28 23:52:13.634811 IP6 fe80::5054:ff:fef1:6bf4 > ip6-allrouters: ICMP6, router solicitation, length 16 23:52:13.634861 IP6 :: > ff02::1:fff1:6bf4: ICMP6, neighbor solicitation, who has fe80::5054:ff:fef1:6bf4, length 24 23:52:13.634944 IP6 fe80::5054:ff:fef1:6bf4 > ff02::16: HBH ICMP6, multicast listener report v2, 1 group record(s), length 28 23:52:13.637932 IP6 :: > ff02::16: HBH ICMP6, multicast listener report v2, 1 group record(s), length 28 23:52:13.637973 IP6 fe80::5054:ff:fef1:6bf4 > ip6-allrouters: ICMP6, router solicitation, length 16 23:52:13.638066 IP6 :: > ff02::1:fff1:6bf4: ICMP6, neighbor solicitation, who has fe80::5054:ff:fef1:6bf4, length 24 23:52:13.638133 IP6 fe80::5054:ff:fef1:6bf4 > ff02::16: HBH ICMP6, multicast listener report v2, 1 group record(s), length 28
3, 此时，将radvd打开，ssh连接立马断开。但此时虚机里的默认路由还在。
23:53:13.273412 IP6 2001:db8:0:1:5054:ff:fe42:13a9 > ip6-allnodes: ICMP6, neighbor advertisement, tgt is 2001:db8:0:1:5054:ff:fe42:13a9, length 32 23:53:13.273490 IP6 2001:db8:0:1:5054:ff:fe42:13a9 > ip6-allnodes: ICMP6, neighbor advertisement, tgt is 2001:db8:0:1:5054:ff:fe42:13a9, length 32 23:53:13.273568 IP6 fe80::5054:ff:fe42:13a9 > ff02::16: HBH ICMP6, multicast listener report v2, 1 group record(s), length 28 23:53:13.273613 IP6 fe80::5054:ff:fe42:13a9 > ff02::16: HBH ICMP6, multicast listener report v2, 1 group record(s), length 28 23:53:13.273678 IP6 2001:db8:0:1:5054:ff:fe42:13a9 > ip6-allnodes: ICMP6, neighbor advertisement, tgt is 2001:db8:0:1:5054:ff:fe42:13a9, length 32 23:53:13.273756 IP6 2001:db8:0:1:7056:5fff:fe91:74b > ip6-allnodes: ICMP6, neighbor advertisement, tgt is 2001:db8:0:1:7056:5fff:fe91:74b, length 32 23:53:13.273835 IP6 2001:db8:0:1:5054:ff:fe42:13a9 > ip6-allnodes: ICMP6, neighbor advertisement, tgt is 2001:db8:0:1:5054:ff:fe42:13a9, length 32 23:53:13.273913 IP6 2001:db8:0:1:5054:ff:fe42:13a9 > ip6-allnodes: ICMP6, neighbor advertisement, tgt is 2001:db8:0:1:5054:ff:fe42:13a9, length 32 23:53:13.273995 IP6 fe80::8c42:64ff:fed7:fc4f > ip6-allnodes: ICMP6, router advertisement, length 56 23:53:13.274040 IP6 2001:db8:0:1:5054:ff:fe42:13a9 > ip6-allnodes: ICMP6, neighbor advertisement, tgt is 2001:db8:0:1:5054:ff:fe42:13a9, length 32 23:53:13.274098 IP6 2001:db8:0:1:5054:ff:fe42:13a9 > ip6-allnodes: ICMP6, neighbor advertisement, tgt is 2001:db8:0:1:5054:ff:fe42:13a9, length 32 23:53:13.274183 IP6 2001:db8:0:1:7056:5fff:fe91:74b > ip6-allnodes: ICMP6, neighbor advertisement, tgt is 2001:db8:0:1:7056:5fff:fe91:74b, length 32 23:53:13.274263 IP6 2001:db8:0:1:7056:5fff:fe91:74b > ip6-allnodes: ICMP6, neighbor advertisement, tgt is 2001:db8:0:1:7056:5fff:fe91:74b, length 32 23:53:13.274379 IP6 2001:db8:0:1:5054:ff:fe42:13a9 > ip6-allnodes: ICMP6, neighbor advertisement, tgt is 2001:db8:0:1:5054:ff:fe42:13a9, length 32 23:53:13.274438 IP6 2001:db8:0:1:7056:5fff:fe91:74b > ip6-allnodes: ICMP6, neighbor advertisement, tgt is 2001:db8:0:1:7056:5fff:fe91:74b, length 32 23:53:13.274523 IP6 fe80::8c42:64ff:fed7:fc4f > ip6-allnodes: ICMP6, router advertisement, length 56
4, 再关闭radvd，ssh连接无法恢复，此时虚机里的默认路由丢失，虚机里报大量的这种错“ICMPv6: RA: ndisc_router_discovery failed to add default route”。此时，虚机奇慢无比，只能强制重启。