On carriers whose attach PDN is granted IPv4-only (Odido, Swisscom, O2 UK
so far) the modem refuses every AP-side IPv6 bearer request made by APN
string with pdn-ipv6-call-disallowed before it reaches the air, so the
ims PDN never came up and imsd looped. A request made by 3GPP profile
index is treated as the IMS-class call the modem's own engine makes and
is exempt: it goes on the air as IPv6 and the network grants it. That is
the path 81voltd uses.
Look the ims profile up by APN in the modem's profile list and create the
bearer with profile-id=<index>,ip-type=<type>; fall back to the APN string
when no such profile exists. A profile-indexed bearer reports no APN, so
the reuse match accepts the profile id too. New knobs in /etc/imsd.env:
IMS_APN (default ims) and IMS_PROFILE_ID (default: looked up; "none"
forces the APN-string path).
Verified on KPN with the wall induced by a forced IPv4 attach: the
APN-string request is refused, the profile-indexed request connects, a
second run reuses the bearer, imsd registers over it; attach and mobile
data untouched.
Three hardenings, each of which cost a field-debugging round-trip:
- Every mmcli failure now lands in the journal verbatim (create-bearer
and connect stderr were swallowed, making 'connect attempt N failed'
undecodable — no-service and interface-in-use looked identical).
- Connect attempts are gated on network registration (up to
IMS_REG_TIMEOUT, default 300 s): the 10x10 s window is shorter than
some carriers' post-boot attach (~2 min measured), so every attempt
could burn out before the network was even attached. The settled
modem/packet-service state is logged either way.
- Bearer ip-type is configurable via IMS_IP_TYPE in /etc/imsd.env
(default ipv6); the bearer find/reuse now matches ip-type too, so a
config change cannot silently reuse a stale bearer of the old type.
TimeoutStartSec grows 600->900 to cover the registration gate.
Tested on the FP6 dev phone (KPN): clean-state bring-up in 4 s;
gate + timeout path with modem disabled; per-attempt error lines on a
real contested-PDN failure (second ims PDN while one is connected);
idempotent reuse + REGISTERED (fresh) via systemd.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Userspace VoLTE/IMS daemon for mainline Linux phones (developed on the
Fairphone 6): a GLib-free core (SIP, SDP, USIM AKA, IPsec SA setup, RTP
media, call engine) behind a GDBus control daemon, a standalone AMR-WB
media leg, and a Plasma Dialer backend. C++26 modules built with Crafter
Build; the tree is clean under the project's house-style linter
(crafter-build lint) across all three build products.
Assisted-by: Claude:claude-fable-5
Signed-off-by: Jorijn van der Graaf <jorijnvdgraaf@catcrafts.net>
