Beginner error on my part : there are debug logs in networkd, I didn't even check them. As often, it turns out part of the answer lies in there.
Here are the logs from 2.33: autopkgtest systemd-networkd[942]: test_eth42: Gained IPv6LL autopkgtest systemd-networkd[942]: test_eth42: link_check_ready(): DHCP4, DHCP6 or IPv4LL is enabled but no dynamic address is assigned yet. autopkgtest systemd-networkd[942]: test_eth42: Discovering IPv6 routers autopkgtest systemd-networkd[942]: NDISC: Started IPv6 Router Solicitation client autopkgtest systemd-networkd[942]: test_eth42: Remembering foreign route: dst: fe80::dcad:beff:feef:4711/128, src: n/a, gw: n/a, prefsrc: n/a, scope: global, table: local(255), proto: kernel, type: local, nexthop: 0 autopkgtest systemd-networkd[942]: NDISC: Sent Router Solicitation, next solicitation in 4s autopkgtest systemd-networkd[942]: rtnl: received non-static neighbor, ignoring. autopkgtest systemd-networkd[942]: NDISC: Received Router Advertisement: flags MANAGED preference medium lifetime 1800 sec autopkgtest systemd-networkd[942]: NDISC: Invoking callback for 'router' event. autopkgtest systemd-networkd[942]: DHCPv6 CLIENT: Started in Managed mode autopkgtest systemd-networkd[942]: test_eth42: Acquiring DHCPv6 lease on NDisc request autopkgtest systemd-networkd[942]: test_eth42: Configuring route: dst: n/a, src: n/a, gw: fe80::6051:85ff:fe70:4c03, prefsrc: n/a, scope: global, table: main(254), proto: ra, type: unicast, nexthop: 0 And the equivalent in 2.34: Aug 27 14:28:27 autopkgtest systemd-networkd[939]: test_eth42: Gained IPv6LL Aug 27 14:28:27 autopkgtest systemd-networkd[939]: test_eth42: link_check_ready(): DHCP4, DHCP6 or IPv4LL is enabled but no dynamic address is assigned yet. Aug 27 14:28:27 autopkgtest systemd-networkd[939]: test_eth42: Discovering IPv6 routers Aug 27 14:28:27 autopkgtest systemd-networkd[939]: NDISC: Started IPv6 Router Solicitation client Aug 27 14:28:27 autopkgtest systemd-networkd[939]: test_eth42: Remembering foreign route: dst: fe80::dcad:beff:feef:4711/128, src: n/a, gw: n/a, prefsrc: n/a, scope: global, table: local(255), proto: kernel, type: local, nexthop: 0 Aug 27 14:28:29 autopkgtest systemd-networkd[939]: NDISC: Sent Router Solicitation, next solicitation in 4s Aug 27 14:28:29 autopkgtest systemd-networkd[939]: rtnl: received non-static neighbor, ignoring. Aug 27 14:28:29 autopkgtest systemd-networkd[939]: NDISC: Unexpected error while reading from ICMPv6, ignoring: Exchange full Looking through the code, one can trace the EXFULL error to this function: https://github.com/systemd/systemd/blob/main/src/basic/socket- util.c#L1260 Which checks the msg flags and finds MSG_CTRUNC. The thing is, the recvmsg in strace looks like this: recvmsg(20, {msg_name={sa_family=AF_INET6, sin6_port=htons(0), sin6_flowinfo=htonl(0), inet_pton(AF_INET6, "fe80::6051:85ff:fe70:4c03", &sin6_addr), sin6_scope_id=if_nametoindex("test_eth42")}, msg_namelen=128->28, msg_iov=[{iov_base="\206\0000\276@\300\7\10\0\0\0\0\0\0\0\0\3\4@\200\377\377\377\377\377\377\377\377\0\0\0\0"..., iov_len=88}], msg_iovlen=1, msg_control=[{cmsg_len=20, cmsg_level=SOL_SOCKET, cmsg_type=SO_TIMESTAMP_OLD, cmsg_data={tv_sec=1630055833, tv_usec=877754}}, {cmsg_len=16, cmsg_level=SOL_IPV6, cmsg_type=0x34}], msg_controllen=36, msg_flags=0}, MSG_DONTWAIT) = 88 You'll note the msg_flags=0 at the end. So... What the hell? -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to systemd in Ubuntu. https://bugs.launchpad.net/bugs/1940635 Title: systemd-networkd failing to acquire a DHCP6 lease from dnsmasq on armhf Status in glibc package in Ubuntu: New Status in netplan.io package in Ubuntu: New Status in systemd package in Ubuntu: New Bug description: systemd-networkd is failing to acquire a DCHP6 lease from dnsmasq on armhf since glibc 2.34-0ubuntu1, failing systemd (tests-name=networkd- test.py) and netplan.io (test-name=ethernets) tests on armhf. Reproducer: * Setup an armhf container, e.g. via: autopkgtest systemd --test-name=networkd-test.py --shell -U --apt-pocket=proposed=src:systemd,src:glibc -s -- lxd autopkgtest/ubuntu/impish/armhf * It will fail and drop you into the shell * cd test/ && apt install python3-nose * nosetests3 -v -s -m "test_.*_dhcp_ip6" networkd-test.py This is unrelated to the recent dnsmasq changes (LP: #1894619), as that would fail on all architectures, not just armhf. It still passes inside an amd64 LXD container, so it is also not related to armhf being tested inside a container. But it shows the difference between armhf vs amd64 container, that on armhf we're missing the DHCPSOLICIT (and therefore DHCPREPLY) messages, as can be seen from the dnsmasq log: dnsmasq-dhcp[]: DHCPSOLICIT(router_eth42) 00:02:00:00:ab:11:57:1e:20:2f:9e:56:5f:34 dnsmasq-dhcp[]: DHCPREPLY(router_eth42) 2600::1f 00:02:00:00:ab:11:57:1e:20:2f:9e:56:5f:34 autopkgtest-lxd-rtypaf The issue is most probably the same that causes the currently failing netplan.io/ethernets autopkgtest on armhf, if tested against glibc 2.34-0ubuntu1. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/glibc/+bug/1940635/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
