04 kannel

Date: 2026-09-05. Repo commit: 9c4939f (working tree, phase 4 changes uncommitted on top). Host Docker: 29.6.2. Images: interop-kannel:1.4.5-12 (debian:bookworm-20260824-slim + kannel=1.4.5-12, four config variants), nicolaka/netshoot:v0.16 (capture sidecar and tshark), node:24.18.0-bookworm-slim (test runner, from the root compose.yaml).

Setup

Four bearerbox+smsbox pairs, one Docker image, four config variants under interop-tests/peers/kannel/ (main.conf, iv33.conf, maxpending1.conf, notransceiver.conf), all dialling the same node:2775. Only the main variant's link is captured (each container only sees its own veth). Submits go in over smsbox's sendsms HTTP API; MO and DLR callbacks come out to a tiny HTTP receiver in kannel.test.ts (/mo, /mo/iv33, /mo/maxp1, /mo/notrx, /dlr).

Two snags fixed while building the harness, both in the compose/config layer, not the peer:

smsbox's HTTP client to the sms-service get-url and to dlr-url occasionally lost the connect race under this sandbox's networking ("Socket not connected", no retry by default). Added http-request-retry = 3 / http-queue-delay = 1 to every smsbox group.
1.4.5-12 refuses one group = smsc block that sets both port and receive-port ("deprecated" option combination) - notransceiver.conf's separate TX/RX bind needs two group = smsc blocks sharing one smsc-id, one with port, one with receive-port, not one block with both.

Two runs of ./interop-tests/run.py kannel, back to back, both exit 0, both tests 21, pass 21, fail 0:

run 1: frames 60,  submit_sm 11/submit_sm_resp 8, deliver_sm 11/11, enquire_link 8/8,  generic_nack 1
run 2: frames 66,  submit_sm 11/submit_sm_resp 8, deliver_sm 12/12, enquire_link 10/10, generic_nack 1

malformed: 0, expert errors: 0, both runs. submit_sm outrunning submit_sm_resp and the varying enquire_link count are the wait-ack-expiry scenario (below), not a defect - it deliberately holds a response past Kannel's wait-ack window and lets Kannel reconnect.

Scenarios (PLAN.md)

Id	Result	Evidence
S1 (binds 34, submits, receipts, MO)	pass	`kannel main variant - bind`; `S1 - MT from Kannel with delivery reports` (DELIVERED/UNDELIVERABLE/EXPIRED/ENROUTE); `MO to Kannel`
S1 (interface_version 0x33 sub-case, target 8)	pass	`iv33 variant - interface_version 0x33`: binds at 33, no TLVs on the receipt, still correlates
S6 (idle/keepalive)	pass	`S6 - wait-ack expiry and keepalive`: `enquire_link` every 5s keeps a 40s `idleTimeout` session alive; a deliberately-late `sendResp()` past `wait-ack` (5s) is recorded, not asserted against (Kannel's own choice, see below)
S11 (encodings, target 12)	pass	`€ [ ] ~ round trip through Kannel unpacked GSM7`; long GSM and UCS-2 (with 一 and an emoji) MT reassembly
target 11 (window)	pass	`maxp1 variant - max-pending-submits 1`: 20 sendsms calls, `max-pending-submits = 1`, all 20 arrive in order, none dropped or duplicated
target 8 (separate TX/RX)	pass	`notrx variant - separate TX and RX binds`: transmitter + receiver binds; submit_sm and MO/receipt only ever cross the intended bind

Wire facts

dlr-mask=31's %d is not one code per SMPP state. Kannel fires two HTTP callbacks per settled message: type=8 off the submit_sm_resp alone (before any receipt, answer=ACK/), then a final one. DELIVERED is type=1, ENROUTE is type=4, UNDELIVERABLE is type=2 - but EXPIRED is type=34 (32|2), its own bit, not folded into the generic failure code. A receiver keying only on 1/2/4/8 will misfile an expired message as unhandled.
%P (destination) is smsbox's own global-sender, not the message's real destination. With no my-number set on the smsc group, an MO's %P reports the smsbox group's global-sender value verbatim (here 46700000000), not the deliver_sm's destination_addr. %p (source) additionally gets a + prepended for an international-TON address even though the wire address carried none; %P gets no such +.
%a (MO text) is decoded for GSM but raw for UCS-2. For a GSM-coded MO, %a is the decoded human-readable string, safe to percent-decode as UTF-8. For UCS-2 (coding=2), %a is the raw big-endian UCS-2 bytes, percent-escaped byte-for-byte (一 → %4E%00, a lone surrogate half → %D8%3D etc.) - not re-encoded as UTF-8 first. A receiver that runs URLSearchParams.get('text') (or any UTF-8-aware percent-decoder) on a coding=2 callback gets mojibake, since those bytes are not valid UTF-8. The receiver must percent-decode to a raw byte buffer and UCS-2-decode it itself, branching on coding. (This tripped the test harness itself first - kannel.test.ts's MO receiver now does exactly this via moText()/percentDecodeBytes().)
A submit_sm in the wrong direction gets generic_nack, not a mismatched *_resp. Calling session.sendSms() on a link where Kannel is the ESME (submit_sm only flows ESME→SMSC) gets answered with generic_nack carrying ESME_RINVCMDID - not a submit_sm_resp. Confirmed in the capture (frame with command_id 0x80000000 immediately answering a 0x00000004). session.sendSms()'s result surfaces this the same way it would a submit_sm_resp error (result.err.message matches ESME_RINVCMDID), so nothing here needed different handling - but a caller matching on response command id specifically would need to accept both.
interface-version = "33" negotiates cleanly. No TLVs sent either way, receipts still carry id:/stat: text and still correlate to the right smsId.
wait-ack expiry disconnects and reconnects, it does not retry in place. Holding a submit_sm response past Kannel's wait-ack (5s here) makes bearerbox log an I/O error and redial; the late response lands on a session Kannel has already abandoned and is harmlessly ignored. Kannel's own reaction, not a length this suite enforces.
max-pending-submits = 1 is a strict one-at-a-time link. A burst of sendsms calls all still arrive, in the order smsbox forwarded them, but only as fast as this side answers each submit_sm - the whole burst stalls behind an unanswered first message. Answering immediately (not batching responses) is required to observe the burst complete at all.

Defects in @larvit/smpp

None found against Kannel across two clean runs (21/21 both times). Two bugs surfaced during this phase were both in the test harness, not src/, and are already fixed in kannel.test.ts:

The MO-text UTF-8-vs-raw-UCS2 decoding gap described above (moText/percentDecodeBytes).
The max-pending-submits=1 burst test originally deferred every sendResp() to the end of the test; under a window of 1, Kannel can't advance past the first unanswered submit_sm, so the burst never arrived. Fixed by answering each sms as it lands.

Open questions

Whether type=34 for EXPIRED is Kannel-version-specific, or whether REJECTD/DELETED have their own similarly-unfolded bits - only EXPIRED was exercised here.
Whether the raw-bytes-for-UCS2 %a behaviour also applies to dlr-url's equivalent fields, or is MO-specific - not exercised here (this suite's dlr-url never carries message text).

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