iwlwifi driver losts icmpv6 router advertisement packages

[Peter Muss]

I use netplan together network manager.
After a while my computer lost its default route for ipv6. When investigating with tcpdump on another client (raspberry pi) I found that my router sends an icmpv6 router advertisement message about every 8-10 minutes, but my computer only receives 30-50% of the router advertisement messages.
The wifi connection is stable and has a reception strength of around 80%. A ping6 with 1000 messages works without any packet loss. If no router advertisement message is received after 1800 seconds, the ipv6 default route disappears.
A second computer with intel wifi hardware that still runs with kernel 5.4.0-91-generic but uses a different wifi chipset has the same problems. I also tested the mainline kernels 5.15.11 and 5.16.0-rc7. Still the same behavior with the other kernels. I don't see any error message in syslog or dmesg while a packet is lost.
If I exchange my wifi hardware to an ALFA Network AWUS036ACH, then all packets are received and the default route stays stable.

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> sysctl net.ipv6.conf.wlp3s0
net.ipv6.conf.wlp3s0.accept_dad = 1
net.ipv6.conf.wlp3s0.accept_ra = 1
net.ipv6.conf.wlp3s0.accept_ra_defrtr = 1
net.ipv6.conf.wlp3s0.accept_ra_from_local = 0
net.ipv6.conf.wlp3s0.accept_ra_min_hop_limit = 1
net.ipv6.conf.wlp3s0.accept_ra_mtu = 1
net.ipv6.conf.wlp3s0.accept_ra_pinfo = 1
net.ipv6.conf.wlp3s0.accept_ra_rt_info_max_plen = 0
net.ipv6.conf.wlp3s0.accept_ra_rt_info_min_plen = 0
net.ipv6.conf.wlp3s0.accept_ra_rtr_pref = 1
net.ipv6.conf.wlp3s0.accept_redirects = 1
net.ipv6.conf.wlp3s0.accept_source_route = 0
net.ipv6.conf.wlp3s0.addr_gen_mode = 0
net.ipv6.conf.wlp3s0.autoconf = 1
net.ipv6.conf.wlp3s0.dad_transmits = 1
net.ipv6.conf.wlp3s0.disable_ipv6 = 0
net.ipv6.conf.wlp3s0.disable_policy = 0
net.ipv6.conf.wlp3s0.drop_unicast_in_l2_multicast = 0
net.ipv6.conf.wlp3s0.drop_unsolicited_na = 0
net.ipv6.conf.wlp3s0.enhanced_dad = 1
net.ipv6.conf.wlp3s0.force_mld_version = 0
net.ipv6.conf.wlp3s0.force_tllao = 0
net.ipv6.conf.wlp3s0.forwarding = 0
net.ipv6.conf.wlp3s0.hop_limit = 255
net.ipv6.conf.wlp3s0.ignore_routes_with_linkdown = 0
net.ipv6.conf.wlp3s0.keep_addr_on_down = 0
net.ipv6.conf.wlp3s0.max_addresses = 16
net.ipv6.conf.wlp3s0.max_desync_factor = 600
net.ipv6.conf.wlp3s0.mc_forwarding = 0
net.ipv6.conf.wlp3s0.mldv1_unsolicited_report_interval = 10000
net.ipv6.conf.wlp3s0.mldv2_unsolicited_report_interval = 1000
net.ipv6.conf.wlp3s0.mtu = 1492
net.ipv6.conf.wlp3s0.ndisc_notify = 0
net.ipv6.conf.wlp3s0.ndisc_tclass = 0
net.ipv6.conf.wlp3s0.proxy_ndp = 0
net.ipv6.conf.wlp3s0.regen_max_retry = 3
net.ipv6.conf.wlp3s0.router_probe_interval = 60
net.ipv6.conf.wlp3s0.router_solicitation_delay = 1
net.ipv6.conf.wlp3s0.router_solicitation_interval = 4
net.ipv6.conf.wlp3s0.router_solicitation_max_interval = 3600
net.ipv6.conf.wlp3s0.router_solicitations = -1
net.ipv6.conf.wlp3s0.rpl_seg_enabled = 0
net.ipv6.conf.wlp3s0.seg6_enabled = 0
net.ipv6.conf.wlp3s0.seg6_require_hmac = 0
sysctl: Zugriff verweigert auf Schlüssel »net.ipv6.conf.wlp3s0.stable_secret«
net.ipv6.conf.wlp3s0.suppress_frag_ndisc = 1
net.ipv6.conf.wlp3s0.temp_prefered_lft = 86400
net.ipv6.conf.wlp3s0.temp_valid_lft = 604800
net.ipv6.conf.wlp3s0.use_oif_addrs_only = 0
net.ipv6.conf.wlp3s0.use_tempaddr = 1
#################################################################
A lost packet recorded on another client (raspberry pi) with
> tcpdump -n -vv -i wlan0 icmp6 and 'ip6[40] = 134'

22:03:52.766917 IP6 (flowlabel 0x236ab, hlim 255, next-header ICMPv6 (58) payload length: 144) fe80::464e:6dff:fe42:d85d > ff02::1: [icmp6 sum ok] ICMP6, router advertisement, length 144
        hop limit 255, Flags [managed, other stateful], pref high, router lifetime 1800s, reachable time 0ms, retrans timer 0ms
          prefix info option (3), length 32 (4): 2003:d1:bf19:600::/64, Flags [onlink, auto], valid time 7200s, pref. time 1800s
            0x0000: 40c0 0000 1c20 0000 0708 0000 0000 2003
            0x0010: 00d1 bf19 0600 0000 0000 0000 0000
          prefix info option (3), length 32 (4): fd05:7501:b88f::/64, Flags [onlink, auto], valid time 0s, pref. time 0s
            0x0000: 40c0 0000 0000 0000 0000 0000 0000 fd05
            0x0010: 7501 b88f 0000 0000 0000 0000 0000
          rdnss option (25), length 24 (3): lifetime 1200s, addr: fe80::c0ff:7ee3:779b:6b31
            0x0000: 0000 0000 04b0 fe80 0000 0000 0000 c0ff
            0x0010: 7ee3 779b 6b31
          mtu option (5), length 8 (1): 1492
            0x0000: 0000 0000 05d4
          route info option (24), length 8 (1): ::/0, pref=high, lifetime=1800s
            0x0000: 0008 0000 0708
          route info option (24), length 16 (2): 2003:d1:bf19:600::/56, pref=high, lifetime=1800s
            0x0000: 3808 0000 0708 2003 00d1 bf19 0600
          source link-address option (1), length 8 (1): 44:4e:6d:42:d8:5d
            0x0000: 444e 6d42 d85d
###################################################################
Routing with default route

> ip -6 route show dev wlp3s0
2003:d1:bf19:600::/64 proto kernel metric 256 expires 6948sec pref medium
fe80::/64 proto kernel metric 256 pref medium
default via fe80::464e:6dff:fe42:d85d proto ra metric 1024 expires 1548sec mtu 1492 hoplimit 255 pref high

###################################################################
Routing without default route

>ip -6 route show dev wlp3s0
2003:d1:bf19:600::/64 proto kernel metric 256 expires 5382sec pref medium
fe80::/64 proto kernel metric 256 pref medium

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: linux-image-5.11.0-43-generic 5.11.0-43.47~20.04.2
ProcVersionSignature: Ubuntu 5.11.0-43.47~20.04.2-generic 5.11.22
Uname: Linux 5.11.0-43-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.21
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: KDE
Date: Thu Dec 30 20:52:55 2021
InstallationDate: Installed on 2020-05-01 (608 days ago)
InstallationMedia: Kubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
SourcePackage: linux-signed-hwe-5.11
UpgradeStatus: No upgrade log present (probably fresh install)