Dibbler-client fails to bind on ppp interfaces, fails to install, fails to build on Ubuntu 22.04

[Radek Zajic]

Before I start: I know that the author of Dibbler considers this software unmaintained (https://klub.com.pl/dhcpv6/); yet it is included in the repositories, so here I am with this bug report.

== Issue #1: Dibbler binds to incorrect link-local address of a ppp(oe) interface ==
After upgrading my home router from Ubuntu 20.04 to Ubuntu 22.04, I have noticed that dibbler-client is no longer capable of starting up and binding to the PPPoE (PPP) interface created as part of my connection set-up process.

This is how the link local addresses look like:
rzajic@router:/home/work/dibbler/dibbler-1.0.1$ ip -6 a s dev ppp999 scope link
28: ppp999: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1492 qdisc cake state UNKNOWN group default qlen 3
    inet6 fe80::8157:b42e:45ec:96ae peer fe80::427c:7dff:fe93:d231/128 scope link
       valid_lft forever preferred_lft forever

fe80::8157:b42e:45ec:96ae is my side of the point to point link
fe80::427c:7dff:fe93:d231 is the ISP side of the point to point link
(The addresses change on every reconnection, it's nothing sensitive.)

The error logs from Dibbler-client were:

Apr 25 11:00:39 router.local systemd[1]: Starting LSB: Starts DHCPv6 client...
Apr 25 11:00:39 router.local dibbler-client[86944]: Starting DHCPv6 client: dibbler-client.
Apr 25 11:00:39 router.local systemd[1]: Started LSB: Starts DHCPv6 client.
Apr 25 11:00:39 router.local DibblerClient[86950]: PD: Following interfaces marked as downlink: br0.2
Apr 25 11:00:39 router.local DibblerClient[86950]: Prefix delegation option (no parameters) found.
Apr 25 11:00:39 router.local DibblerClient[86950]: Parsing /etc/dibbler/client.conf done, result=0(success)
Apr 25 11:00:39 router.local DibblerClient[86950]: 1 interface(s) specified in /etc/dibbler/client.conf
Apr 25 11:00:39 router.local DibblerClient[86950]: Interface ppp999/28 configuration has been loaded.
Apr 25 11:00:39 router.local DibblerClient[86950]: DUID's value = 00:01:00:01:27:3c:48:99:40:8d:5c:b3:2a:ab was loaded from client-duid file.
Apr 25 11:00:39 router.local DibblerClient[86950]: My DUID is 00:01:00:01:27:3c:48:99:40:8d:5c:b3:2a:ab.
Apr 25 11:00:39 router.local DibblerClient[86950]: Loading old address database (client-AddrMgr.xml), using built-in routines.
Apr 25 11:00:39 router.local DibblerClient[86950]: Unable to open client-AddrMgr.xml.
Apr 25 11:00:39 router.local DibblerClient[86950]: Bind reuse enabled (multiple instances allowed).
Apr 25 11:00:39 router.local DibblerClient[86950]: Creating control (::) socket on the lo/1 interface.
Apr 25 11:00:39 router.local DibblerClient[86950]: Creating socket (addr=fe80::427c:7dff:fe93:d231) on ppp999/28 interface.
Apr 25 11:00:39 router.local DibblerClient[86950]: Unable to bind socket (iface=ppp999/28, addr=fe80::427c:7dff:fe93:d231, port=546).
Apr 25 11:00:39 router.local DibblerClient[86950]: Low-level layer error message: Unable to bind socket: Cannot assign requested address
Apr 25 11:00:39 router.local DibblerClient[86950]: Socket creation (addr=fe80::427c:7dff:fe93:d231) on ppp999/28 interface failed.
Apr 25 11:00:39 router.local DibblerClient[86950]: Fatal error during TransMgr initialization.

After a quick review, it became clear that the dibbler-client attempts to bind to incorrect IPv6 link local address. This might be related to how the new(er?) clients present the link local addresses.

Using the script from https://raw.githubusercontent.com/d0u9/examples/master/C/netlink/ip_show.c, I can see that the link local address on my side of the point to point link is now represented as "local address", while on non-point to point links the link local addresses are represented as interface addresses.

==================================
family: 6
dev: ppp999
prefix length: 128

local address: fe80::8157:b42e:45ec:96ae (flags 128, scope 253)
if address: fe80::427c:7dff:fe93:d231 (flags 128, scope 253)

==================================
family: 6
dev: tap4
prefix length: 64

if address: fe80::4048:1aff:fe2e:64f4 (flags 128, scope 253)

This can be worked around by modifying the low level Linux code (note that there seems to be a bug in Dibbler code, which uses IFLA_ADDRESS [belongs to layer 2, e.g. MAC address] instead of IFA_ADDRESS):
--- lowlevel-linux.c 2022-04-25 23:56:08.736090768 +0200
+++ dibbler-1.0.1/Port-linux/lowlevel-linux.c 2022-04-25 23:30:35.889052974 +0200
@@ -277,7 +277,7 @@
      if (!rta_tb[IFA_LOCAL]) rta_tb[IFA_LOCAL] = rta_tb[IFA_ADDRESS];
      if (!rta_tb[IFA_ADDRESS]) rta_tb[IFA_ADDRESS] = rta_tb[IFA_LOCAL];

- memcpy(addr,(char*)RTA_DATA(rta_tb[IFLA_ADDRESS]),16);
+ memcpy(addr,(char*)RTA_DATA(rta_tb[IFA_LOCAL]),16);
      if (addr[0]!=0xfe || addr[1]!=0x80) {
   continue; /* ignore non link-scoped addrs */
      }

The local address is always set a few lines above the memcpy() call.

After rebuild (see Issue #3 below), the process starts, binds and request a prefix (which was my goal at the beginning):

Apr 25 23:39:45 router.local systemd[1]: Starting LSB: Starts DHCPv6 client...
Apr 25 23:39:45 router.local dibbler-client[243724]: Starting DHCPv6 client: dibbler-client.
Apr 25 23:39:45 router.local systemd[1]: Started LSB: Starts DHCPv6 client.
Apr 25 23:39:45 router.local DibblerClient[243730]: PD: Following interfaces marked as downlink: br0.2
Apr 25 23:39:45 router.local DibblerClient[243730]: Prefix delegation option (no parameters) found.
Apr 25 23:39:45 router.local DibblerClient[243730]: Parsing /etc/dibbler/client.conf done, result=0(success)
Apr 25 23:39:45 router.local DibblerClient[243730]: 1 interface(s) specified in /etc/dibbler/client.conf
Apr 25 23:39:45 router.local DibblerClient[243730]: Interface ppp999/28 configuration has been loaded.
Apr 25 23:39:45 router.local DibblerClient[243730]: DUID's value = 00:01:00:01:27:3c:48:99:40:8d:5c:b3:2a:ab was loaded from client-duid file.
Apr 25 23:39:45 router.local DibblerClient[243730]: My DUID is 00:01:00:01:27:3c:48:99:40:8d:5c:b3:2a:ab.
Apr 25 23:39:45 router.local DibblerClient[243730]: Loading old address database (client-AddrMgr.xml), using built-in routines.
Apr 25 23:39:45 router.local DibblerClient[243730]: DB timestamp:1650922785, now()=1650922785, db is 0 second(s) old.
Apr 25 23:39:45 router.local DibblerClient[243730]: Auth: Replay detection value loaded 0
Apr 25 23:39:45 router.local DibblerClient[243730]: All client's 00:01:00:01:27:3c:48:99:40:8d:5c:b3:2a:ab leases are not valid.
Apr 25 23:39:45 router.local DibblerClient[243730]: Bind reuse enabled (multiple instances allowed).
Apr 25 23:39:45 router.local DibblerClient[243730]: Creating control (::) socket on the lo/1 interface.
Apr 25 23:39:45 router.local DibblerClient[243730]: DEBUG: realIface: <IfaceIface name="ppp999" ifindex="28" hwType="512" flags="0x110d1" mBit="0" oBit="0">
                                                        <!-- no-loopback running multicast -->
                                                        <!-- PrefixLength configured to 128 -->
                                                        <!-- 1 link scoped addrs -->
                                                        <Addr>fe80::8157:b42e:45ec:96ae</Addr>
                                                        <!-- 3 non-local addrs -->
                                                        2001:1ae9:ff2:xxxx::1 2001:1ae9:ff2:xxxx:faf0:100c:edd5:ed6d 2001:1ae9:ff2:xxxx:8157:b42e:45ec:96ae <Mac></Mac>
                                                      </IfaceIface>
                                                    , Interface
Apr 25 23:39:45 router.local DibblerClient[243730]: Creating socket (addr=fe80::8157:b42e:45ec:96ae) on ppp999/28 interface.
Apr 25 23:39:45 router.local DibblerClient[243730]: Initialising link-state detection for interfaces: ppp999/28
Apr 25 23:39:45 router.local DibblerClient[243730]: CONFIRM support compiled in.
Apr 25 23:39:45 router.local DibblerClient[243730]: Creating SOLICIT message with 0 IA(s), no TA and 1 PD(s) on ppp999/28 interface.
Apr 25 23:39:45 router.local DibblerClient[243730]: Sending SOLICIT(opts:1 25 8 ) on ppp999/28 to multicast.
Apr 25 23:39:45 router.local DibblerClient[243730]: Sleeping for 1 second(s).
Apr 25 23:39:45 router.local DibblerClient[243730]: Received 81 bytes on interface ppp999/28 (socket=3, addr=fe80::427c:7dff:fe93:d231).
Apr 25 23:39:45 router.local DibblerClient[243730]: Received ADVERTISE on ppp999/28,trans-id=0x655732, 3 opts: 2 1 25
Apr 25 23:39:45 router.local DibblerClient[243730]: Script execution skipped for ADVERTISE response to SOLICIT. No action needed for this message type.
Apr 25 23:39:45 router.local DibblerClient[243730]: Sleeping for 1 second(s).
Apr 25 23:39:46 router.local DibblerClient[243730]: Processing msg (SOLICIT,transID=0x655732,opts: 1 25 8)
Apr 25 23:39:46 router.local DibblerClient[243730]: Creating REQUEST. Backup server list contains 1 server(s).
Apr 25 23:39:46 router.local DibblerClient[243730]: Advertise from Server ID=00:03:00:01:40:7c:7d:93:d2:31, no preference option, assumed 0.[using this]
Apr 25 23:39:46 router.local DibblerClient[243730]: Sending REQUEST(opts:1 25 2 8 ) on ppp999/28 to multicast.
Apr 25 23:39:46 router.local DibblerClient[243730]: Sleeping for 1 second(s).
Apr 25 23:39:46 router.local DibblerClient[243730]: Received 81 bytes on interface ppp999/28 (socket=3, addr=fe80::427c:7dff:fe93:d231).
Apr 25 23:39:46 router.local DibblerClient[243730]: Received REPLY on ppp999/28,trans-id=0xd529db, 3 opts: 2 1 25
Apr 25 23:39:46 router.local DibblerClient[243730]: PD: Adding 2001:1ae9:xxxx:xx00:: prefix to PD (iaid=1) to addrDB.
Apr 25 23:39:46 router.local DibblerClient[243730]: PD: Adding prefix 2001:1ae9:xxxx:xx00::/56 to all interfaces (prefix will be split to /64 prefixes if necessary).
Apr 25 23:39:46 router.local DibblerClient[243730]: PD: Using 1 suitable interface(s):br0.2
Apr 25 23:39:46 router.local DibblerClient[243730]: PD: Adding prefix 2001:1ae9:xxxx:xx00::/56 on the br0.2/13 interface.
Apr 25 23:39:46 router.local DibblerClient[243730]: RENEW(IA_PD) will be sent (T1) after 1800, REBIND (T2) after 2880 seconds.
Apr 25 23:39:46 router.local DibblerClient[243730]: About to execute /etc/dibbler/client-notify.sh script, 15 variables.
Apr 25 23:39:46 router.local DibblerClient[243730]: Script execution complete, return code=0
Apr 25 23:39:46 router.local DibblerClient[243730]: Sleeping for 1799 second(s).

== Issue #2: Post-install script fails ==

This is yet another issue spotted as part of the installation. Maybe it would deserve a separate bug report - who knows. Anyway, here it is:

The postinst script fails, causing the whole installation to fail:
Preparing to unpack .../dibbler-client_1.0.1-1build2_amd64.deb ...
Unpacking dibbler-client (1.0.1-1build2) over (1.0.1-1build2) ...
Setting up dibbler-client (1.0.1-1build2) ...
Error: The new file /etc/dibbler/client.conf-dpkg-new does not exist!
dpkg: error processing package dibbler-client (--install):
 installed dibbler-client package post-installation script subprocess returned error exit status 1
Processing triggers for man-db (2.10.2-1) ...
Errors were encountered while processing:
 dibbler-client

This can be fixed by creating the conf-new version at all times:
--- dibbler-client.postinst 2022-04-25 23:52:28.891596403 +0200
+++ /home/work/dibbler/dibbler-1.0.1/debian/dibbler-client.postinst 2022-04-25 23:39:40.203950174 +0200
@@ -30,6 +30,8 @@
     rm ${CONFFILE_NEW}
 fi

+touch ${CONFFILE_NEW}
+
 db_version 2.0
 #db_capb backup
 db_settitle dibbler-client/title

== Issue #3: Dibbler rebuild fails ==
To rebuild the package on Ubuntu 22.04 with the latest gcc, I had to supply the "-fcommon" flag explicitly:

apt-get source dibbler-client
apt-get build-deps dibbler-client
cd dibbler-1.0.1/
DEB_CPPFLAGS_SET="-fcommon" DEB_CFLAGS_SET="-fcommon" debuild -us -uc -i -b

Without that backwards compatibility flag, build fails on this error:
/usr/bin/ld: libLowLevel_a-interface.o (symbol from plugin): in function `daemon_log':
(.text+0x0): multiple definition of `interface_do_message'; libLowLevel_a-lowlevel-linux-link-state.o (symbol from plugin):(.text+0x0): first defined here
/usr/bin/ld: libLowLevel_a-interface.o (symbol from plugin): in function `daemon_log':
(.text+0x0): multiple definition of `interface_auto_up'; libLowLevel_a-lowlevel-linux-link-state.o (symbol from plugin):(.text+0x0): first defined here
./Port-linux/daemon.h:30:5: warning: 'die' violates the C++ One Definition Rule [-Wodr]
   30 | int die(const char * pidfile);
      | ^
Port-linux/daemon.cpp:191:6: note: return value type mismatch
  191 | void die(const char * pidfile) {
      | ^
Port-linux/daemon.cpp:191:6: note: type 'void' should match type 'int'
Port-linux/daemon.cpp:191:6: note: 'die' was previously declared here
collect2: error: ld returned 1 exit status
make[2]: *** [Makefile:629: dibbler-client] Error 1
make[2]: Leaving directory '/home/work/dibbler/dibbler-1.0.1'
make[1]: *** [Makefile:816: all-recursive] Error 1
make[1]: Leaving directory '/home/work/dibbler/dibbler-1.0.1'
dh_auto_build: error: make -j1 returned exit code 2
make: *** [debian/rules:16: build] Error 25
dpkg-buildpackage: error: debian/rules build subprocess returned exit status 2
debuild: fatal error at line 1182:
dpkg-buildpackage -us -uc -ui -i -b failed

== System info ==
# lsb_release -rd
Description: Ubuntu 22.04 LTS
Release: 22.04

# Shows my rebuild/patched version
# apt-cache policy dibbler-client
dibbler-client:
  Installed: 1.0.1-1build2
  Candidate: 1.0.1-1.1
  Version table:
     1.0.1-1.1 500
        500 http://cz.archive.ubuntu.com/ubuntu jammy/universe amd64 Packages
 *** 1.0.1-1build2 100
        100 /var/lib/dpkg/status