- C++ 93.2%
- Shell 6.8%
| Filename | Latest commit message | Latest commit date |
|---|---|---|
Jorijn van der Graaf
828b0af95b
The README had grown to 422 lines: the device and carrier table came after 61 lines of architecture, and the configuration section after 237 lines of architecture, that table, build, run and packaging notes and GNOME Calls detail. AGENTS.md, a file for coding agents, takes that detail and adds to it: a reference to the tree at this commit, written from the code and the bench record. The README is now what a person needs: what imsd is and its status, the verified device/carrier table, what it needs, how to install and enable it, the two dialers, a status check for the installed daemon, a `Not there yet` list, and where the rest is. In-tree comments that sent readers to README sections which moved — the cross-compiling flow (the CI workflow, build-package.sh, APKBUILD.binary), GNOME Calls' known gaps (imsd-ofono-restart-calls.sh), the D-Bus ABI (main.cpp) and the Configuration section (imsd.service) — point at AGENTS.md's sections now. |
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| .forgejo/workflows | ||
| implementations | ||
| interfaces | ||
| packaging | ||
| tests | ||
| .gitignore | ||
| AGENTS.md | ||
| LICENSE | ||
| lint-rules.h | ||
| Makefile | ||
| project.cpp | ||
| README.md | ||
imsd
Userspace IMS/VoLTE daemon for mainline Linux phones.
Modem firmware on typical mainline-Linux phones will bring up the IMS PDN but can't be used for actual call audio. imsd implements the whole IMS client in userspace instead: SIP registration with USIM AKA authentication over kernel IPsec (ESP), call signalling, and the AMR-WB RTP media plane wired into PipeWire so a stock mobile dialer — Plasma Dialer, or GNOME Calls under Phosh and GNOME Mobile — can place and receive real VoLTE calls on a commercial network.
Status
Call-capable, both directions: outgoing calls place, answer, carry full-duplex
AMR-WB audio and tear down; incoming calls ring, answer and carry media the
same way, driven end-to-end from a stock dialer over a frozen D-Bus ABI.
Not there yet: DTMF (SendDtmf is a stub), hold/multiparty/call waiting,
USSD, P-CSCF discovery (the address is configured by hand).
Verified by community members to be fully working:
| Device | OS | Carrier |
|---|---|---|
| The Fairphone (Gen. 6) | postmarketOS, Linux 7.1.2 | KPN NL |
| The Fairphone (Gen. 6) | postmarketOS, Linux 7.1.2 | Telekom Deutschland GER |
| The Fairphone (Gen. 6) | postmarketOS, Linux 7.1.2 | Phonero |
| The Fairphone (Gen. 6) | postmarketOS, Linux 7.1.2 | Telia Norge |
What it needs
imsd talks to the modem through ModemManager plus qmicli over QRTR, installs
its security associations with ip xfrm and plays audio through PipeWire, so
in practice: a Qualcomm modem on a mainline kernel with working
WWAN/ModemManager integration, kernel ESP, PipeWire, systemd and polkit — and
your carrier's P-CSCF address.
Install and configure
On a Catcrafts Fairphone 6 image imsd is installed from the project's apk
registry and upgrades with apk upgrade (an upgrade restarts the daemon; a
call in progress ends). Elsewhere, build it (below), make install, and
enable the units yourself — systemctl enable imsd, and systemctl enable --now imsd-ofonod for GNOME Calls: imsd's preset, the
multi-user.target.wants link and the /etc/imsd.env condition below come
with the apk, not with make install.
Configuration is environment variables in /etc/imsd.env; the one required
setting is the P-CSCF:
# your carrier's P-CSCF address — from a stock-firmware capture or the
# carrier's IMS documentation
PCSCF=2001:db8::105
The apk's imsd.service is enabled by preset and starts at boot once that
file exists (the condition is checked when the unit starts, so after writing
the file run systemctl start imsd). It first brings the ims PDN up through ModemManager, then registers:
resuming an existing registration when it can, registering fresh otherwise,
and waiting out whatever the network tells it to wait out. Check on it with:
journalctl -u imsd -f
busctl --system call net.catcrafts.IMS1 /net/catcrafts/IMS1 net.catcrafts.IMS1 GetStatus
Every variable, what the daemon does when the registration breaks, and what the journal lines mean are in AGENTS.md (§10, §7.4, §7.8).
Dialers
imsd itself is desktop-agnostic: everything a dialer needs is on the system
bus as net.catcrafts.IMS1. A small translation daemon per desktop speaks
the backend protocol its dialer already consumes, so dialer, shell and the
call-history/contacts stack run unmodified.
| Desktop | Daemon | Package | Owns | Consumed by |
|---|---|---|---|---|
| Plasma Mobile | imsd-dialerd |
imsd |
org.kde.telephony.* (session bus) |
plasma-dialer + kde-telephony-daemon, replacing modem-daemon |
| Phosh / GNOME Mobile | imsd-ofonod |
imsd-ofono |
org.ofono (system bus) |
GNOME Calls' ofono provider plugin |
Plasma Mobile needs nothing beyond the imsd package: imsd-dialerd is
autostarted in the session in place of plasma-dialer's modem-daemon, whose
own autostart must be off — the package hides it for accounts created after
the install (/etc/skel); an existing account hides it itself with a
Hidden=true copy of org.kde.modem.daemon.desktop in ~/.config/autostart.
For Phosh and GNOME Mobile, apk add imsd-ofono enables imsd-ofonod and
points GNOME Calls at its ofono provider (a gschema override; the per-user
equivalent is gsettings set org.gnome.Calls autoload-plugins "['ofono']").
Do not run it alongside a real ofonod. Known gaps — USSD, hold and
multiparty, caller-ID withholding, the empty emergency-call screen, and why a
restart of imsd-ofonod restarts GNOME Calls — are listed in
AGENTS.md §8.3.
Call control is polkit's net.catcrafts.IMS1.Voice: the active local
session and root may place, answer and end calls; an ssh login may not.
Building
Crafter Build plus clang/libc++/lld and the gio-2.0 headers:
crafter-build # the daemon; -- --product=media|dialerd|ofonod for the others
crafter-build test # the seven unit-test suites
make && make check # the same, without crafter-build (distro packaging)
Cross-compiling for a phone, the Makefile's requirements, the package layout and the CI that publishes the apks are in AGENTS.md (§4, §9).
Documentation
AGENTS.md is the complete reference — for coding agents, and for anyone who wants to know how imsd works or change it: the build products and the rule that keeps the engine core free of GLib and I/O, the test suites, the lint rules, the registration and recovery behaviour, the ims PDN bring-up, upgrades, the frozen D-Bus ABI, packaging and release mechanics, the full configuration reference, and the carrier behaviours the code was shaped by.
License
GPL-3.0-only — see LICENSE.
Copyright
Copyright (C) 2026 Catcrafts® catcrafts.net