MINOR: h3: simplify GOAWAY local emission

Rework GOAWAY emission handling at the HTTP/3 layer. Previously, h3c
member <id_goaway> were updated during the connection on each new
streams attach. This ID was finally reused when a GOAWAY was emitted.

However, this is unnecessary to keep an updated ID during the connection
lifetime. Indeed, <largest_bidi_r> QCC member can be used for the same
purpose. Note that this is only useful for the frontend side. For a
client connection, GOAWAY contains a PUSH ID, thus 0 can be used for
now.

Thus, <id_goaway> in h3c is renamed <id_shut_l>. Now it is only sent
when the GOAWAY is emitted. This allows to reject any streams with a
greater ID. This approach is considered simpler.

Note that <largest_bidi_r> is not strictly similar to the obsolete
<id_goaway>. Indeed, if an error occurs before the corresponding stream
layer allocation, the former would still be incremented. However,
this is not a real issue as GOAWAY specification is clear that lower IDs
are not guaranteed to being handled well, until either the stream is
closed or resetted, or the whole connection is teared down.

diff --git a/src/h3.c b/src/h3.c
index 6a4798791666bc1621a2e9f332d9822276a82510..77f8bb91ef3ccebfbbc963a3aa48d7d2197082ad 100644 (file)
--- a/src/h3.c
+++ b/src/h3.c
@@ -140,7 +140,7 @@ struct h3c {
        uint64_t qpack_blocked_streams;
        uint64_t max_field_section_size;
 
-       uint64_t id_goaway; /* stream ID used for a GOAWAY frame */
+       uint64_t id_shut_l; /* GOAWAY ID locally emitted */
 
        struct buffer_wait buf_wait; /* wait list for buffer allocations */
        /* Stats counters */
@@ -611,7 +611,6 @@ static ssize_t h3_req_headers_to_htx(struct qcs *qcs, const struct buffer *buf,
        struct ist meth = IST_NULL, path = IST_NULL;
        struct ist scheme = IST_NULL, authority = IST_NULL;
        struct ist uri;
-       uint64_t id_goaway;
        int hdr_idx, ret;
        int cookie = -1, last_cookie = -1, i;
        int relaxed = !!(h3c->qcc->proxy->options2 & PR_O2_REQBUG_OK);
@@ -1059,27 +1058,7 @@ static ssize_t h3_req_headers_to_htx(struct qcs *qcs, const struct buffer *buf,
        htx_to_buf(htx, &htx_buf);
        htx = NULL;
 
-       /* Stream attach may need the new GOAWAY ID, so update it before.
-        * Keep a copy of the older value to restore it in case of error.
-        */
-       id_goaway = h3c->id_goaway;
-
-       /* RFC 9114 5.2. Connection Shutdown
-        *
-        * The GOAWAY frame contains an identifier that
-        * indicates to the receiver the range of requests or pushes that were
-        * or might be processed in this connection.  The server sends a client-
-        * initiated bidirectional stream ID; the client sends a push ID.
-        * Requests or pushes with the indicated identifier or greater are
-        * rejected (Section 4.1.1) by the sender of the GOAWAY.  This
-        * identifier MAY be zero if no requests or pushes were processed.
-        */
-       if (qcs->id >= h3c->id_goaway)
-               h3c->id_goaway = qcs->id + 4;
-
        if (qcs_attach_sc(qcs, &htx_buf, fin)) {
-               /* Stream not handled, restore old GOAWAY ID. */
-               h3c->id_goaway = id_goaway;
                len = -1;
                goto out;
        }
@@ -3106,7 +3085,7 @@ static int h3_attach(struct qcs *qcs, void *conn_ctx)
         * The endpoint SHOULD continue to do so as more requests or
         * pushes arrive.
         */
-       if (h3c->flags & H3_CF_GOAWAY_SENT && qcs->id >= h3c->id_goaway &&
+       if (h3c->flags & H3_CF_GOAWAY_SENT && qcs->id >= h3c->id_shut_l &&
            quic_stream_is_bidi(qcs->id)) {
                /* Local stack should not attached stream on a closed connection. */
                BUG_ON(quic_stream_is_local(qcs->qcc, qcs->id));
@@ -3148,11 +3127,22 @@ static int h3_send_goaway(struct h3c *h3c)
        struct qcs *qcs = h3c->ctrl_strm;
        struct buffer pos, *res;
        unsigned char data[3 * QUIC_VARINT_MAX_SIZE];
-       size_t frm_len = quic_int_getsize(h3c->id_goaway);
+       uint64_t id_goaway;
+       size_t frm_len;
        size_t xfer;
 
        TRACE_ENTER(H3_EV_H3C_END, h3c->qcc->conn);
 
+       /* RFC 9114 5.2. Connection Shutdown
+        *
+        * The GOAWAY frame contains an identifier that
+        * indicates to the receiver the range of requests or pushes that were
+        * or might be processed in this connection. The server sends a client-
+        * initiated bidirectional stream ID; the client sends a push ID.
+        */
+       id_goaway = !conn_is_back(h3c->qcc->conn) ?
+         h3c->qcc->largest_bidi_r : 0;
+
        if (!qcs) {
                TRACE_ERROR("control stream not initialized", H3_EV_H3C_END, h3c->qcc->conn);
                goto err;
@@ -3160,9 +3150,10 @@ static int h3_send_goaway(struct h3c *h3c)
 
        pos = b_make((char *)data, sizeof(data), 0, 0);
 
+       frm_len = quic_int_getsize(id_goaway);
        b_quic_enc_int(&pos, H3_FT_GOAWAY, 0);
        b_quic_enc_int(&pos, frm_len, 0);
-       b_quic_enc_int(&pos, h3c->id_goaway, 0);
+       b_quic_enc_int(&pos, id_goaway, 0);
 
        res = qcc_get_stream_txbuf(qcs, &err, 0);
        if (!res || b_room(res) < b_data(&pos) ||
@@ -3175,6 +3166,7 @@ static int h3_send_goaway(struct h3c *h3c)
        xfer = b_force_xfer(res, &pos, b_data(&pos));
        qcc_send_stream(qcs, 1, xfer);
 
+       h3c->id_shut_l = id_goaway;
        h3c->flags |= H3_CF_GOAWAY_SENT;
        TRACE_LEAVE(H3_EV_H3C_END, h3c->qcc->conn);
        return 0;
@@ -3183,6 +3175,7 @@ static int h3_send_goaway(struct h3c *h3c)
        /* Consider GOAWAY as sent even if not really the case. This will
         * block future stream opening using H3_REQUEST_REJECTED reset.
         */
+       h3c->id_shut_l = id_goaway;
        h3c->flags |= H3_CF_GOAWAY_SENT;
        TRACE_DEVEL("leaving in error", H3_EV_H3C_END, h3c->qcc->conn);
        return 1;
@@ -3207,7 +3200,7 @@ static int h3_init(struct qcc *qcc)
        h3c->ctrl_strm = NULL;
        h3c->err = 0;
        h3c->flags = 0;
-       h3c->id_goaway = 0;
+       h3c->id_shut_l = 0;
 
        qcc->ctx = h3c;
        h3c->prx_counters = qc_counters(qcc->conn->target, &h3_stats_module);