netdev - Re: Regression in IPv6 autoconf, maybe "ipv6/addrconf: fix timing bug in tempaddr regen"

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Message-ID: <nr14o635-577n-n3s4-np6n-rp8367ss9n24@vanv.qr>
Date: Fri, 2 Jun 2023 00:23:50 +0200 (CEST)
From: Jan Engelhardt <jengelh@...i.de>
To: Sam Edwards <cfsworks@...il.com>
cc: Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, 
    "David S. Miller" <davem@...emloft.net>
Subject: Re: Regression in IPv6 autoconf, maybe "ipv6/addrconf: fix timing
 bug in tempaddr regen"


On Thursday 2023-06-01 13:51, Jan Engelhardt wrote:
>>> 
>>> I am observing that between kernel 5.19 and 6.0, a change was introduced
>>> that makes the system just stop generating IPv6 Privacy Addresses after
>>> some time.
>>
>> I'd been encountering this exact problem very reliably since at
>> least the early 4.x days [...] but that my patch is evidently
>> making the problem happen *more* frequently in your case!

The Arris/Vodafone TG3442DE router, for unknown and undiagnosable
reasons (blackbox), issues RAs where the prefix is de-advertised
with a lifetime of 0 for a window of about 10-15 seconds. (tcpdump
below)

After the prefix is re-advertised with 86400s lifetime, Linux
clients do not resume address generation. The investigation continues.


2023-06-01 23:15:20.630778 IP6 (flowlabel 0x0452b, hlim 255, next-header ICMPv6 (58) payload length: 128) fe80::f2af:85ff:fe9a:33ec > ff02::1: [icmp6 sum ok] ICMP6, router advertisement, length 128
	hop limit 64, Flags [managed, other stateful], pref medium, router lifetime 1800s, reachable time 3600000ms, retrans timer 0ms
	  rdnss option (25), length 24 (3):  lifetime 300s, addr: 2a02:8108:96bf:f1c4:f2af:85ff:fe9a:33ec
	    0x0000:  0000 0000 012c 2a02 8108 96bf f1c4 f2af
	    0x0010:  85ff fe9a 33ec
	  prefix info option (3), length 32 (4): 2a02:8108:96bf:f1c4::/64, Flags [onlink, auto], valid time 86400s, pref. time 43200s
	    0x0000:  40c0 0001 5180 0000 a8c0 0000 0000 2a02
	    0x0010:  8108 96bf f1c4 0000 0000 0000 0000
	  route info option (24), length 24 (3):  2a02:8108:96bf:f1c4::/62, pref=medium, lifetime=86400s
	    0x0000:  3e00 0001 5180 2a02 8108 96bf f1c4 0000
	    0x0010:  0000 0000 0000
	  route info option (24), length 24 (3):  ::/0, pref=medium, lifetime=1800s
	    0x0000:  0000 0000 0708 0000 0000 0000 0000 0000
	    0x0010:  0000 0000 0000
	  source link-address option (1), length 8 (1): f0:af:85:9a:33:ec
	    0x0000:  f0af 859a 33ec
2023-06-01 23:15:22.001430 IP6 (flowlabel 0x0452b, hlim 255, next-header ICMPv6 (58) payload length: 104) fe80::f2af:85ff:fe9a:33ec > ff02::1: [icmp6 sum ok] ICMP6, router advertisement, length 104
	hop limit 64, Flags [managed, other stateful], pref medium, router lifetime 1800s, reachable time 3600000ms, retrans timer 0ms
	  rdnss option (25), length 24 (3):  lifetime 300s, addr: 2a02:8108:96bf:f1c4:f2af:85ff:fe9a:33ec
	    0x0000:  0000 0000 012c 2a02 8108 96bf f1c4 f2af
	    0x0010:  85ff fe9a 33ec
	  prefix info option (3), length 32 (4): 2a02:8108:96bf:f1c4::/64, Flags [onlink, auto], valid time 0s, pref. time 0s
	    0x0000:  40c0 0000 0000 0000 0000 0000 0000 2a02
	    0x0010:  8108 96bf f1c4 0000 0000 0000 0000
	  route info option (24), length 24 (3):  ::/0, pref=medium, lifetime=1800s
	    0x0000:  0000 0000 0708 0000 0000 0000 0000 0000
	    0x0010:  0000 0000 0000
	  source link-address option (1), length 8 (1): f0:af:85:9a:33:ec
	    0x0000:  f0af 859a 33ec
2023-06-01 23:15:25.003317 IP6 (flowlabel 0x0452b, hlim 255, next-header ICMPv6 (58) payload length: 104) fe80::f2af:85ff:fe9a:33ec > ff02::1: [icmp6 sum ok] ICMP6, router advertisement, length 104
 [same]
2023-06-01 23:15:28.006222 IP6 (flowlabel 0x0452b, hlim 255, next-header ICMPv6 (58) payload length: 104) fe80::f2af:85ff:fe9a:33ec > ff02::1: [icmp6 sum ok] ICMP6, router advertisement, length 104
 [same]
2023-06-01 23:15:31.010397 IP6 (flowlabel 0x0452b, hlim 255, next-header ICMPv6 (58) payload length: 104) fe80::f2af:85ff:fe9a:33ec > ff02::1: [icmp6 sum ok] ICMP6, router advertisement, length 104
 [same]
2023-06-01 23:15:32.576848 IP6 (flowlabel 0x0452b, hlim 255, next-header ICMPv6 (58) payload length: 128) fe80::f2af:85ff:fe9a:33ec > ff02::1: [icmp6 sum ok] ICMP6, router advertisement, length 128
	hop limit 64, Flags [managed, other stateful], pref medium, router lifetime 1800s, reachable time 3600000ms, retrans timer 0ms
	  rdnss option (25), length 24 (3):  lifetime 300s, addr: 2a02:8108:96bf:f1c4:f2af:85ff:fe9a:33ec
	    0x0000:  0000 0000 012c 2a02 8108 96bf f1c4 f2af
	    0x0010:  85ff fe9a 33ec
	  prefix info option (3), length 32 (4): 2a02:8108:96bf:f1c4::/64, Flags [onlink, auto], valid time 86400s, pref. time 43200s
	    0x0000:  40c0 0001 5180 0000 a8c0 0000 0000 2a02
	    0x0010:  8108 96bf f1c4 0000 0000 0000 0000
	  route info option (24), length 24 (3):  2a02:8108:96bf:f1c4::/62, pref=medium, lifetime=86400s
	    0x0000:  3e00 0001 5180 2a02 8108 96bf f1c4 0000
	    0x0010:  0000 0000 0000
	  route info option (24), length 24 (3):  ::/0, pref=medium, lifetime=1800s
	    0x0000:  0000 0000 0708 0000 0000 0000 0000 0000
	    0x0010:  0000 0000 0000
	  source link-address option (1), length 8 (1): f0:af:85:9a:33:ec
	    0x0000:  f0af 859a 33ec