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net: qrtr: forward data packets between endpoints (FP6 voice prototype)

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The DSP subsystems are star-connected through the application
processor: each has a qrtr link to us but none to each other. Incoming
packets whose dst_node is neither the local node nor broadcast are
currently delivered to a *local* port matching dst_port (usually
nothing) and dropped, so two remote DSPs can never exchange QMI
messages.

On the FP6 (SM7635, AudioReach) the modem's voice stack needs exactly
that: it must reach the ADSP's service-registry notifier / audio
service to attach the vocoder to a VCPM voice session. Without
forwarding, every voice graph starts cleanly but the modem never
streams a single mailbox packet - calls stay silent both ways (see
journal/calls.md 2026-07-07/08).

Forward DATA and RESUME_TX packets destined to another known node onto
that node's endpoint, re-using qrtr_node_enqueue for per-hop flow
control. RESUME_TX additionally releases this hop's flow token on the
arrival link; per-hop counters stay in lockstep with end-to-end ones
because every packet of a forwarded flow transits this node. Control
packets keep flowing to the local ns, which already redistributes
service announcements mesh-wide.

Prototype for the milos carry; needs discussion (loop prevention,
broadcast handling, flow-control semantics) before any upstream
attempt.

Assisted-by: Claude:claude-fable-5
Signed-off-by: Jorijn van der Graaf <jorijnvdgraaf@catcrafts.net>
This commit is contained in:
Jorijn van der Graaf 2026-07-07 20:07:01 +02:00
commit 0c63174949
1 changed files with 48 additions and 0 deletions
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48
net/qrtr/af_qrtr.c
View file

@ -520,6 +520,54 @@ int qrtr_endpoint_post(struct qrtr_endpoint *ep, const void *data, size_t len)
qrtr_node_assign(node, le32_to_cpu(pkt->server.node));
}
/* The DSPs are star-connected through this node: forward packets
* destined to another node onto that node's endpoint (e.g. the
* modem's voice stack talking to the ADSP's audio service). Only
* DATA and RESUME_TX transit; control packets keep going to the
* local ns, which does its own mesh-wide redistribution. RESUME_TX
* additionally releases this hop's flow-control token on the
* arrival link: per-hop counters advance in lockstep with the
* end-to-end ones since every packet of the flow transits here.
*/
if (cb->dst_node != qrtr_local_nid &&
cb->dst_node != QRTR_NODE_BCAST &&
(cb->type == QRTR_TYPE_DATA || cb->type == QRTR_TYPE_RESUME_TX)) {
struct sockaddr_qrtr from = {AF_QIPCRTR,
cb->src_node, cb->src_port};
struct sockaddr_qrtr to = {AF_QIPCRTR,
cb->dst_node, cb->dst_port};
struct qrtr_node *dst;
dst = qrtr_node_lookup(cb->dst_node);
if (!dst || dst == node) {
if (dst)
qrtr_node_release(dst);
goto err;
}
if (cb->type == QRTR_TYPE_RESUME_TX) {
struct sk_buff *clone;
clone = skb_clone(skb, GFP_ATOMIC);
if (clone)
qrtr_tx_resume(node, clone);
}
pr_debug("qrtr: fwd %u:%u -> %u:%u type %d len %zu\n",
cb->src_node, cb->src_port,
cb->dst_node, cb->dst_port, cb->type, size);
if (skb_cow_head(skb, sizeof(struct qrtr_hdr_v1))) {
qrtr_node_release(dst);
goto err;
}
qrtr_node_enqueue(dst, skb, cb->type, &from, &to);
qrtr_node_release(dst);
return 0;
}
if (cb->type == QRTR_TYPE_RESUME_TX) {
qrtr_tx_resume(node, skb);
} else {