[Bug 1853669] Re: systemd resolves own hostname to link local ipv6 address
Andreas L
avl.ramschbox at gmx.at
Fri Dec 6 16:18:11 UTC 2019
/etc/hosts:
127.0.0.1 localhost
127.0.1.1 kato i7
# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
$ systemd-resolve --status
Global
DNS Servers: 10.2.2.3
DNSSEC NTA: 10.in-addr.arpa
16.172.in-addr.arpa
168.192.in-addr.arpa
17.172.in-addr.arpa
18.172.in-addr.arpa
19.172.in-addr.arpa
20.172.in-addr.arpa
21.172.in-addr.arpa
22.172.in-addr.arpa
23.172.in-addr.arpa
24.172.in-addr.arpa
25.172.in-addr.arpa
26.172.in-addr.arpa
27.172.in-addr.arpa
28.172.in-addr.arpa
29.172.in-addr.arpa
30.172.in-addr.arpa
31.172.in-addr.arpa
corp
d.f.ip6.arpa
home
internal
intranet
lan
local
private
test
Link 2 (enp4s0)
Current Scopes: none
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: no
Remark: I have no idea where these ##.172.in-addr.arpa come from.
$ systemd-resolve fpc
fpc: 10.2.2.1%enp4s0
10.2.2.250%enp4s0
fe80::4687:fcff:fe9e:4ac7%2%enp4s0
-- Information acquired via protocol DNS in 1.6ms.
-- Data is authenticated: yes
Remark: ah, here it still has the network-name along with the ipv6
$ systemd-resolve -t A fpc
fpc IN A 10.2.2.1 # interface enp4s0
fpc IN A 10.2.2.250 # interface enp4s0
-- Information acquired via protocol DNS in 2.2ms.
-- Data is authenticated: yes
$ systemd-resolve -t AAAA fpc
fpc IN AAAA fe80::4687:fcff:fe9e:4ac7 # interface enp4s0
-- Information acquired via protocol DNS in 2.1ms.
-- Data is authenticated: yes
Remark: ah, here it also has the network-name along with the ipv6
$ dig @10.2.2.3 -t A fpc
; <<>> DiG 9.11.3-1ubuntu1.11-Ubuntu <<>> @10.2.2.3 -t A fpc
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 57577
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1280
;; QUESTION SECTION:
;fpc. IN A
;; ANSWER SECTION:
fpc. 0 IN A 10.2.2.1
;; Query time: 0 msec
;; SERVER: 10.2.2.3#53(10.2.2.3)
;; WHEN: Fri Dec 06 17:11:19 CET 2019
;; MSG SIZE rcvd: 48
Remark: As I said, upstream DNS 10.2.2.3 doesn't know about the second
10.2.2.250 address.
$ dig @10.2.2.3 -t AAAA fpc
; <<>> DiG 9.11.3-1ubuntu1.11-Ubuntu <<>> @10.2.2.3 -t AAAA fpc
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 924
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;fpc. IN AAAA
;; Query time: 0 msec
;; SERVER: 10.2.2.3#53(10.2.2.3)
;; WHEN: Fri Dec 06 17:12:03 CET 2019
;; MSG SIZE rcvd: 21
Remark: As I said, upstream DNS 10.2.2.3 doesn't know about inet6 link
local addresses.
$ dig @127.0.0.53 -t A fpc
; <<>> DiG 9.11.3-1ubuntu1.11-Ubuntu <<>> @127.0.0.53 -t A fpc
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 7210
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;fpc. IN A
;; ANSWER SECTION:
fpc. 0 IN A 10.2.2.1
fpc. 0 IN A 10.2.2.250
;; Query time: 0 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Fri Dec 06 17:15:14 CET 2019
;; MSG SIZE rcvd: 64
Remark: systemd-resolved DOES obtain this info elsewhere than from
upstream DNS.
$ dig @127.0.0.53 -t AAAA fpc
; <<>> DiG 9.11.3-1ubuntu1.11-Ubuntu <<>> @127.0.0.53 -t AAAA fpc
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 45149
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;fpc. IN AAAA
;; ANSWER SECTION:
fpc. 0 IN AAAA fe80::4687:fcff:fe9e:4ac7
;; Query time: 0 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Fri Dec 06 17:16:16 CET 2019
;; MSG SIZE rcvd: 60
Remark: systemd-resolved DOES obtain this info elsewhere than from
upstream DNS.
--
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https://bugs.launchpad.net/bugs/1853669
Title:
systemd resolves own hostname to link local ipv6 address
Status in systemd package in Ubuntu:
Incomplete
Bug description:
I've got an ethernet-device that only has a configured ipv4 address,
and some auto-generated link-local (aka "scope link") ipv6 address.
Any tool doing a DNS query (and /lib/systemd/systemd-resolved is the
DNS-server listening on 127.0.0.53) for this host's hostname gets back
two addresses: the correct ipv4 address, and a broken ipv6 address.
Unlike on ipv4, it is possible for the same ipv6-address to be
assigned to multiple devices, and therefore the address is only valid
in the context of the eth-device.
Now, if "ifconfig" shows "inet6 fe80::4687:fcff:fe9e:4ac7 prefixlen 64 scopeid 0x20<link>"
then "fe80::4687:fcff:fe9e:4ac7" is NOT a connectable address, and syscall connect() typically fails with EINVAL.
To make it a valid address, it needs to be suffixed with a "%" and the device name, like:
fe80::4687:fcff:fe9e:4ac7%enp4s0
Either the resolver can return the link name attached to the address
separated with a "%" char, or it needs to ignore link-local inet6
addresses.
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