On Thu, Jan 8, 2026 at 10:36 AM Paolo Abeni [off-list ref] wrote:

On 1/5/26 3:04 PM, Xin Long wrote:

quoted

+/* Create and register new streams for sending or receiving. */
+static struct quic_stream *quic_stream_create(struct quic_stream_table *streams,
+                                           s64 max_stream_id, bool send, bool is_serv)
+{
+     struct quic_stream_limits *limits = &streams->send;
+     struct quic_stream *stream = NULL;
+     gfp_t gfp = GFP_KERNEL_ACCOUNT;
+     s64 stream_id;
+
+     if (!send) {
+             limits = &streams->recv;
+             gfp = GFP_ATOMIC | __GFP_ACCOUNT;
+     }
+     stream_id = limits->next_bidi_stream_id;
+     if (quic_stream_id_uni(max_stream_id))
+             stream_id = limits->next_uni_stream_id;
+
+     /* rfc9000#section-2.1: A stream ID that is used out of order results in all streams
+      * of that type with lower-numbered stream IDs also being opened.
+      */
+     while (stream_id <= max_stream_id) {
+             stream = kzalloc(sizeof(*stream), gfp);
+             if (!stream)
+                     return NULL;

Do you need to release the allocated ids in case of failure? It would be
sourprising to find some ids allocated when this call fails/returns NULL.

I was aware of this, but didn't change it. As the streams are always opened
sequentially, I think it's fine just to leave them without causing problems
when users assume these streams are not yet open.

quoted

+
+             stream->id = stream_id;
+             if (quic_stream_id_uni(stream_id)) {
+                     if (send) {
+                             stream->send.max_bytes = limits->max_stream_data_uni;
+                     } else {
+                             stream->recv.max_bytes = limits->max_stream_data_uni;
+                             stream->recv.window = stream->recv.max_bytes;
+                     }
+                     /* Streams must be opened sequentially. Update the next stream ID so the
+                      * correct starting point is known if an out-of-order open is requested.
+                      */
+                     limits->next_uni_stream_id = stream_id + QUIC_STREAM_ID_STEP;
+                     limits->streams_uni++;
+
+                     quic_stream_add(streams, stream);
+                     stream_id += QUIC_STREAM_ID_STEP;
+                     continue;
+             }
+
+             if (quic_stream_id_local(stream_id, is_serv)) {
+                     stream->send.max_bytes = streams->send.max_stream_data_bidi_remote;
+                     stream->recv.max_bytes = streams->recv.max_stream_data_bidi_local;
+             } else {
+                     stream->send.max_bytes = streams->send.max_stream_data_bidi_local;
+                     stream->recv.max_bytes = streams->recv.max_stream_data_bidi_remote;
+             }
+             stream->recv.window = stream->recv.max_bytes;
+
+             limits->next_bidi_stream_id = stream_id + QUIC_STREAM_ID_STEP;
+             limits->streams_bidi++;
+
+             quic_stream_add(streams, stream);
+             stream_id += QUIC_STREAM_ID_STEP;
+     }
+     return stream;
+}
+
+/* Check if a send or receive stream ID is already closed. */
+static bool quic_stream_id_closed(struct quic_stream_table *streams, s64 stream_id, bool send)
+{
+     struct quic_stream_limits *limits = send ? &streams->send : &streams->recv;
+
+     if (quic_stream_id_uni(stream_id))
+             return stream_id < limits->next_uni_stream_id;
+     return stream_id < limits->next_bidi_stream_id;

I can't recall if I mentioned the following in a past review... it looks
like the above assumes wrap around are not possible, which is realistic
given the u64 counters - it would require > 100y on a server allocating
4G ids per second.

But it would be nice to explcitly document such assumption somewhere.

How about I add a simple comment in quic_stream_create() right above
the next_uni_stream_id/streams_uni increases, like

"Note overflow of next_uni_stream_id/streams_uni is impossible with u64."

quoted

+}
+
+/* Check if a stream ID would exceed local (recv) or peer (send) limits. */
+bool quic_stream_id_exceeds(struct quic_stream_table *streams, s64 stream_id, bool send)
+{
+     u64 nstreams;
+
+     if (!send) {
+             if (quic_stream_id_uni(stream_id))
+                     return stream_id > streams->recv.max_uni_stream_id;
+             return stream_id > streams->recv.max_bidi_stream_id;
+     }
+
+     if (quic_stream_id_uni(stream_id)) {
+             if (stream_id > streams->send.max_uni_stream_id)
+                     return true;
+             stream_id -= streams->send.next_uni_stream_id;
+             nstreams = quic_stream_id_to_streams(stream_id);

It's not clear to me why send streams only have this additional check.

This is a good question.

For recv.max_uni_stream_id, it changes based on next_uni/bidi_stream_id,
max_streams_uni/bidi and streams_uni/bidi in quic_stream_max_streams_update(),
there's no need to check them again. (maybe I should leave a comment here)

But for send.max_uni_stream_id, it was updated simply from the peer's updated
recv.max_uni_stream_id announcement, it must check its local counts and
limits as well.

quoted

+             return nstreams + streams->send.streams_uni > streams->send./;

Possibly it would be more consistent

max_uni_stream_id -> max_stream_ids_uni

(no strong preferences)

I actually got the variable name from
https://datatracker.ietf.org/doc/html/rfc9000.

quoted

+     }
+
+     if (stream_id > streams->send.max_bidi_stream_id)
+             return true;
+     stream_id -= streams->send.next_bidi_stream_id;
+     nstreams = quic_stream_id_to_streams(stream_id);
+     return nstreams + streams->send.streams_bidi > streams->send.max_streams_bidi;
+}

[...]

quoted

+/* Get or create a receive stream by ID. Requires sock lock held. */
+struct quic_stream *quic_stream_recv_get(struct quic_stream_table *streams, s64 stream_id,
+                                      bool is_serv)
+{
+     struct quic_stream *stream;
+
+     if (!quic_stream_id_valid(stream_id, is_serv, false))
+             return ERR_PTR(-EINVAL);
+
+     stream = quic_stream_find(streams, stream_id);
+     if (stream)
+             return stream;
+
+     if (quic_stream_id_local(stream_id, is_serv)) {
+             if (quic_stream_id_closed(streams, stream_id, true))
+                     return ERR_PTR(-ENOSTR);
+             return ERR_PTR(-EINVAL);
+     }
+
+     if (quic_stream_id_closed(streams, stream_id, false))
+             return ERR_PTR(-ENOSTR);
+
+     if (quic_stream_id_exceeds(streams, stream_id, false))
+             return ERR_PTR(-EAGAIN);
+
+     stream = quic_stream_create(streams, stream_id, false, is_serv);
+     if (!stream)
+             return ERR_PTR(-ENOSTR);
+     if (quic_stream_id_valid(stream_id, is_serv, true))
+             streams->send.active_stream_id = stream_id;

This function is really similar to quic_stream_send_get(), I think it
should be easy factor out a common helper (and possibly use directly
such helper with no send/recv wrapper).

I will factor out a common helper quic_stream_get() but keep
quic_stream_send_get/put() as:

struct quic_stream *quic_stream_send_get(...)
{
        return quic_stream_get(streams, stream_id, is_serv, true);
}

struct quic_stream *quic_stream_recv_get(...)
{
        return quic_stream_get(streams, stream_id, is_serv, false);
}

Thanks.