Jorijn van der Graaf
8b376bbf95
The PGW's router advertisement on the ims netdev offers a default router, and on IPv4-only wifi that is the phone's only IPv6 default route. Every AAAA-first client (apk, browsers) then sends its SYN into the IMS walled garden, which drops it: apk sat in SYN-SENT for nine minutes on the dev phone, and a field user's remedy was to stop imsd before package work. Set accept_ra_defrtr=0 on the muxed netdev before link-up (the router solicitation goes out once the link-local address passes DAD), flush a default route an earlier RA installed (an imsd restart), and give the P-CSCF a host route over the netdev instead. imsd talks to the P-CSCF only and already installs a host route per media peer; the RA's prefix and MTU still apply. The host route makes the P-CSCF reachable before the RA has been processed, so the PDN MTU ModemManager reports is set on the link as well, the way NetworkManager does for its bearers. A failed host route, or a P-CSCF that is not an IPv6 address (the PDN is brought up IPv6-only), fails the unit with a clear message. Dev phone (KPN, 0.3.8-r0): restart path drops the RA default and registers over the host route, apk update in 6 s where it hung; MO and MT calls with audio both ways; cold boot never installs the default route, the link carries the 1280 MTU before the host route exists, fresh registration in 1 s.
303 lines
14 KiB
Shell
303 lines
14 KiB
Shell
#!/bin/sh
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# SPDX-License-Identifier: GPL-3.0-only
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# SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®
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# ims-pdn-up.sh — boot bring-up for the `ims` PDN (journal/ims.md s45).
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#
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# Finds-or-creates the ims bearer via ModemManager, connects it, and
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# configures the muxed netdev with the MM-assigned address (the s34 recipe,
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# automated) and a host route to the P-CSCF — never a default route (F15
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# below). Idempotent — safe to run when the PDN is already up. Runs as
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# ExecStartPre of imsd.service, so imsd only starts once the PDN exists; a
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# nonzero exit fails the unit and systemd retries per Restart/RestartSec.
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#
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# Configuration, via the unit's EnvironmentFile /etc/imsd.env (also read
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# directly so manual runs behave the same):
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# IMS_APN ims APN name (default ims)
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# IMS_IP_TYPE bearer ip-type (default ipv6)
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# IMS_PROFILE_ID 3GPP profile index to connect through (default: looked up
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# by APN in the modem's profile list; empty/none = connect by
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# APN string). A profile-indexed call is exempt from the
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# modem's attach-family forcing that refuses an APN-string
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# IPv6 request when the attach PDN was granted IPv4-only
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# (journal/ims 2026-09-16/17 bench: Odido, O2 UK, Swisscom).
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# IMS_REG_TIMEOUT max seconds to wait for network registration before
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# connect attempts start counting anyway (default 300)
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# PCSCF the P-CSCF address imsd registers with (its own
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# required setting); gets the host route over the ims PDN
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log() { echo "ims-pdn-up: $*"; }
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kv() { mmcli "$@" -K 2>/dev/null; }
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# mmcli's multi-line error text as one journal-friendly line
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squash() { printf '%s' "$1" | tr '\n' ' ' | sed 's/ */ /g'; }
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modem_state() { kv -m "$MODEM" | sed -n 's/^modem\.generic\.state *: *//p'; }
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packet_state() { kv -m "$MODEM" | sed -n 's/^modem\.3gpp\.packet-service-state *: *//p'; }
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bearer_paths() {
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kv -m "$MODEM" | sed -n 's/^modem\.generic\.bearers\.value\[[0-9]*\] *: *//p'
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}
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envval() { # $1 = key — for manual runs; under systemd the vars are inherited
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sed -n "s/^$1=//p" /etc/imsd.env 2>/dev/null | tail -n1 | tr -d '"'
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}
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IP_TYPE=${IMS_IP_TYPE:-$(envval IMS_IP_TYPE)}
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IP_TYPE=${IP_TYPE:-ipv6}
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IMS_APN=${IMS_APN:-$(envval IMS_APN)}
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IMS_APN=${IMS_APN:-ims}
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PROFILE_ID=${IMS_PROFILE_ID:-$(envval IMS_PROFILE_ID)}
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REG_TIMEOUT=${IMS_REG_TIMEOUT:-$(envval IMS_REG_TIMEOUT)}
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REG_TIMEOUT=${REG_TIMEOUT:-300}
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# ---- wait for a modem (MM + modem firmware take a while after boot)
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n=0
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while :; do
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MODEM=$(mmcli -L 2>/dev/null | sed -n 's,.*/Modem/\([0-9]*\).*,\1,p' | head -n1)
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[ -n "$MODEM" ] && break
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n=$((n + 1))
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[ "$n" -ge 60 ] && { log "no modem after 120 s"; exit 1; }
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sleep 2
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done
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log "modem $MODEM"
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# ---- the ims profile index (WDS profile list), unless configured. The
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# lookup itself can fail while ModemManager is still enabling the modem; a
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# failed lookup is not "no profile" (the APN-string request it would fall
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# back to is the one the modem refuses under an IPv4 attach), so it is
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# retried after the registration wait and only a list without the APN
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# falls back to the APN string.
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LOOKUP=pending
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if [ -n "$PROFILE_ID" ]; then
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[ "$PROFILE_ID" = none ] && PROFILE_ID=
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LOOKUP=done
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fi
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lookup_profile() { # $1 = log suffix; sets PROFILE_ID, LOOKUP=done on a usable list
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[ "$LOOKUP" = done ] && return 0
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if OUT=$(qmicli -d qrtr://0 --wds-get-profile-list=3gpp 2>&1); then
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# a list with no profiles at all is the modem still coming up, not
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# a modem without an ims profile (dev phone cold boot 2026-09-20
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# 16:47: exit 0, no entries, index 2 present a minute later)
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if ! printf '%s\n' "$OUT" | grep -q -E '^[[:space:]]*\[[0-9]+\] 3gpp'; then
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log "ims profile lookup returned no profiles$1"
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return 0
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fi
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PROFILE_ID=$(printf '%s\n' "$OUT" | awk -v apn="$IMS_APN" '
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/^[ \t]*\[[0-9]+\] 3gpp/ { idx = $1; gsub(/[^0-9]/, "", idx) }
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/APN:/ { a = $0; sub(/.*APN: '"'"'/, "", a); sub(/'"'"'.*/, "", a);
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if (tolower(a) == tolower(apn) && idx != "") { print idx; exit } }')
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LOOKUP=done
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[ -n "$PROFILE_ID" ] && log "ims profile: index $PROFILE_ID (apn $IMS_APN)" || log "ims profile: none for apn $IMS_APN, connecting by APN string"
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else
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log "ims profile lookup failed$1: $(squash "$OUT")"
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fi
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}
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lookup_profile " (modem state: $(modem_state))"
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# ---- find a connected ims bearer; else find-or-create one and connect it.
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# APN names are case-insensitive. A DISCONNECTED bearer is reused only when
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# it is the request this run would make (same profile index, or same APN when
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# connecting by APN string): a leftover APN-string bearer from a run whose
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# lookup failed is the walled request itself, and reconnecting it fails on
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# every restart until the modem is reset (field: O2 UK, 2026-09-20).
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has() { printf '%s\n' "$INFO" | grep -qi "^bearer\.$1 *: *$2\$"; }
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find_ims_bearer() { # $1 = required bearer.status.connected value; $2 = "relaxed" ignores ip-type
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for B in $(bearer_paths); do
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INFO=$(kv -b "$B") || continue
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has status.connected "$1" || continue
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if [ -n "$PROFILE_ID" ]; then
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if [ "$1" = yes ]; then
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has properties.profile-id "$PROFILE_ID" || has properties.apn "$IMS_APN" || continue
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else
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has properties.profile-id "$PROFILE_ID" || continue
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fi
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else
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has properties.apn "$IMS_APN" || continue
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fi
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[ "$2" = relaxed ] || has properties.ip-type "$IP_TYPE" || continue
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echo "$B"
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return 0
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done
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return 1
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}
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# leftover disconnected APN-string ims bearers when this run connects by
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# profile index: never reused (above), deleted so a later run without an
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# index cannot pick one up either
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delete_stale_bearers() {
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[ -n "$PROFILE_ID" ] || return 0
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for B in $(bearer_paths); do
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INFO=$(kv -b "$B") || continue
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has status.connected no || continue
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has properties.apn "$IMS_APN" || continue
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has properties.profile-id "$PROFILE_ID" && continue
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OUT=$(mmcli -m "$MODEM" --delete-bearer="$B" 2>&1) &&
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log "deleted stale bearer $B (apn $IMS_APN, no profile index)" ||
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log "could not delete stale bearer $B: $(squash "$OUT")"
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done
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}
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BEARER=$(find_ims_bearer yes)
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# ---- gate the connect attempts on network registration: the 10x10 s window
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# below is shorter than some carriers' post-boot attach (measured ~2 min), so
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# without this every attempt can fail on no-service and the retries end
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# before the network is even attached
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if [ -z "$BEARER" ]; then
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waited=0 last=
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while :; do
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STATE=$(modem_state)
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case "$STATE" in registered|connecting|connected) break ;; esac
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[ "$STATE" != "$last" ] && log "waiting for registration (state: ${STATE:-unknown})"
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last=$STATE
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if [ "$waited" -ge "$REG_TIMEOUT" ]; then
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log "not registered after $REG_TIMEOUT s — attempting anyway"
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break
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fi
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sleep 5
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waited=$((waited + 5))
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done
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log "modem state: $(modem_state), packet service: $(packet_state)"
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# a lookup that failed while the modem was still coming up
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n=0
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while [ "$LOOKUP" != done ] && [ "$n" -lt 3 ]; do
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n=$((n + 1))
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sleep 5
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lookup_profile " (retry $n)"
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done
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if [ "$LOOKUP" != done ]; then
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PROFILE_ID=
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log "ims profile: lookup keeps failing, connecting by APN string"
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fi
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BEARER=$(find_ims_bearer yes) # the index may now match a connected profile-indexed PDN
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[ -n "$BEARER" ] || delete_stale_bearers
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fi
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n=0
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while [ -z "$BEARER" ]; do
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n=$((n + 1))
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[ "$n" -gt 10 ] && { log "bearer connect failed after 10 attempts"; exit 1; }
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B=$(find_ims_bearer no) # reuse a stale disconnected ims bearer of this run's shape
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if [ -z "$B" ]; then
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if [ -n "$PROFILE_ID" ]; then
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SPEC="profile-id=$PROFILE_ID,ip-type=$IP_TYPE"
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else
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SPEC="apn=$IMS_APN,ip-type=$IP_TYPE"
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fi
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OUT=$(mmcli -m "$MODEM" --create-bearer="$SPEC" 2>&1)
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B=$(printf '%s' "$OUT" | sed -n 's,.*\(/org/freedesktop/ModemManager1/Bearer/[0-9]*\).*,\1,p')
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if [ -n "$B" ]; then
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log "created bearer $B ($SPEC)"
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else
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log "create-bearer attempt $n failed: $(squash "$OUT"); retrying in 10 s"
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sleep 10
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continue
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fi
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fi
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if OUT=$(mmcli -b "$B" --connect 2>&1); then
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BEARER=$B
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else
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log "connect attempt $n failed (state: $(modem_state)): $(squash "$OUT"); retrying in 10 s"
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case "$OUT" in *call-already-present*)
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# the PDN is up on a bearer this run did not recognise (ip-type or
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# APN spelling); use it rather than ask the modem for a second one
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if B=$(find_ims_bearer yes relaxed); then
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log "adopting the connected bearer $B"
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BEARER=$B
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continue
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fi ;;
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esac
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sleep 10
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fi
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done
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log "connected: $BEARER"
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# ---- configure the muxed netdev with the MM-assigned address
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INFO=$(kv -b "$BEARER")
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IFACE=$(echo "$INFO" | sed -n 's/^bearer\.status\.interface *: *//p')
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ADDR=$(echo "$INFO" | sed -n 's/^bearer\.ipv6-config\.address *: *//p')
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PREFIX=$(echo "$INFO" | sed -n 's/^bearer\.ipv6-config\.prefix *: *//p')
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if [ -z "$IFACE" ] || [ -z "$ADDR" ]; then
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log "bearer up but no interface/address in mmcli output"
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exit 1
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fi
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# ---- the ims PDN must never be the phone's IPv6 default route (F15). The
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# PGW's router advertisement offers a default router; on IPv4-only wifi
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# that is the phone's only v6 default, so every AAAA-first client (apk,
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# browsers) sends its SYN into the IMS walled garden, which drops it
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# silently (dev phone 2026-09-20: a 9-min apk hang). imsd only talks to the
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# P-CSCF (host route below) and to media peers (imsd installs those host
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# routes per call); the RA's prefix and MTU are still applied (its hop
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# limit is not — the kernel default 64 stays). Per-netdev, via /proc, and
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# before link-up: the router solicitation goes out once the link-local
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# address passes DAD, ~1–2 s after link-up, and the RA answers at once.
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if ! echo 0 > "/proc/sys/net/ipv6/conf/$IFACE/accept_ra_defrtr" 2>/dev/null; then
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log "could not set accept_ra_defrtr=0 on $IFACE (continuing)"
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fi
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# the PDN's MTU as the modem reports it (1280 here), on the link itself:
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# the P-CSCF host route makes the P-CSCF reachable before the RA's MTU
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# option has been processed, and a send in that window would otherwise be
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# sized by the link's default MTU. NetworkManager does the same for its
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# bearers. An RA MTU no larger than the link's is still applied.
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MTU=$(echo "$INFO" | sed -n 's/^bearer\.ipv6-config\.mtu *: *//p')
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case "$MTU" in ''|--|*[!0-9]*) MTU= ;; esac
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if [ -n "$MTU" ] && [ "$MTU" -ge 1280 ]; then
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ip link set "$IFACE" mtu "$MTU" || log "could not set mtu $MTU on $IFACE (continuing)"
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fi
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ip link set "$IFACE" up || exit 1
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ip -6 addr replace "$ADDR/${PREFIX:-64}" dev "$IFACE" || exit 1
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# wait out IPv6 DAD: binding a tentative address gives EADDRNOTAVAIL
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# (first boot attempt cost a 120 s systemd retry exactly this way)
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n=0
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while ip -6 addr show dev "$IFACE" | grep -q tentative; do
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n=$((n + 1))
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[ "$n" -ge 10 ] && { log "address still tentative after 10 s"; break; }
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sleep 1
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done
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log "$IFACE up, $ADDR/${PREFIX:-64}, ipv6 mtu $(cat "/proc/sys/net/ipv6/conf/$IFACE/mtu" 2>/dev/null)"
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# a default route an earlier RA already installed (the link was up before
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# this run: an imsd restart) — accept_ra_defrtr=0 leaves an existing one in
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# place until its lifetime runs out. Any ::/0 via this netdev goes, by the
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# policy above.
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if [ -n "$(ip -6 route show default dev "$IFACE" 2>/dev/null)" ]; then
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ip -6 route flush default dev "$IFACE" && log "dropped the RA default route on $IFACE"
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fi
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# the P-CSCF is reachable through the ims PDN only: a host route stands in
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# for the default. `dev` without a gateway — a raw-IP netdev without
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# header_ops, so the kernel resolves no neighbours — the shape imsd uses
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# for media peers. The PDN is brought up IPv6-only (the address above), so
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# the P-CSCF must be an IPv6 address; anything else on the IMS network
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# (its DNS servers, a traceroute target) needs its own host route. Without
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# this route imsd cannot reach the P-CSCF, so a failure is the unit's
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# failure.
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PCSCF=${PCSCF:-$(envval PCSCF)}
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case "$PCSCF" in
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'') log "PCSCF not configured: no P-CSCF host route (imsd needs PCSCF= in /etc/imsd.env)" ;;
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*:*) OUT=$(ip -6 route replace "$PCSCF/128" dev "$IFACE" 2>&1) ||
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{ log "host route to P-CSCF $PCSCF failed: $(squash "$OUT")"; exit 1; }
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log "host route to P-CSCF $PCSCF dev $IFACE" ;;
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*) log "PCSCF '$PCSCF' is not an IPv6 address; the ims PDN is brought up IPv6-only"; exit 1 ;;
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esac
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# ---- hand the connected ims netdev to imsd (imsd.service reads
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# /run/imsd.env) so the daemon carries no baked-in interface name
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echo "DEV=$IFACE" > /run/imsd.env
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# ---- open the IMS protected ports in the firewall (rung 5b root cause,
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# journal/ims.md s56): pmOS's default nftables INPUT chain is policy-drop and
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# explicitly drops all inbound on qmapmux*, which silently killed every
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# network-initiated request (reg-event NOTIFY, MT INVITE) after ESP decap —
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# the P-CSCF's TCP SYNs to the protected server port never reached the
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# listener, so terminating delivery failed and MT calls fell back to CS.
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# 45061/45062 = imsd's protected client/server ports (kPortUc/kPortUs).
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# Best-effort: never fail the unit over a missing/foreign firewall.
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if nft list table inet filter >/dev/null 2>&1; then
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if ! nft list chain inet filter input | grep -q imsd-protected-ports; then
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nft insert rule inet filter input iifname "qmapmux*" tcp dport 45061-45062 accept comment '"imsd-protected-ports"' &&
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nft insert rule inet filter input iifname "qmapmux*" udp dport 45061-45062 accept comment '"imsd-protected-ports"' &&
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log "nftables: opened protected ports 45061-45062 on qmapmux*" ||
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log "nftables: rule insert failed (continuing)"
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fi
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fi
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exit 0
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