invalid checksum in ra6 (regression)

[kuba-moo]

We are using ra6 for linux kernel selftests. We recently migrated our CI system which moved us from manually built ipv6toolkit at 367bbe6 to Fedora-packaged v2.2. This version appears to send RAs with invalid checksums

Before:

../usr/sbin/ra6  -i lo -d 2001:10::1 -P 2001:12::/64
prompt# 21:50:44.587711 IP6 (hlim 255, next-header ICMPv6 (58) payload length: 48) fe80::be42:eb5d:8056:7914 > 2001:10::1: [icmp6 sum ok] ICMP6, router advertisement, length 48
	hop limit 255, Flags [none], pref high, router lifetime 9000s, reachable time 4294967295ms, retrans timer 4000ms
	  prefix info option (3), length 32 (4): 2001:12::/64, Flags [none], valid time infinity, pref. time infinity

v2.2:

# ra6 -i lo -d 2001:10::1 -P 2001:12::/64
21:49:59.440696 IP6 (hlim 255, next-header ICMPv6 (58) payload length: 48) fe80::fb35:de0d:c055:9749 > 2001:10::1: [bad icmp6 cksum 0x95a0 -> 0x9536!] ICMP6, router advertisement, length 48
	hop limit 255, Flags [none], pref high, router lifetime 9000s, reachable time 4294967295ms, retrans timer 4000ms
	  prefix info option (3), length 32 (4): 2001:12::/64, Flags [none], valid time infinity, pref. time infinity