MINOR: h3: do not consider missing buf room as error on trailers

Improve h3_resp_trailers_send() return value to be similar with
h3_resp_data_send(). In particular, if QCS Tx buffer has not enough
space for trailer encoding, 0 is returned instead of an error value,
with QC_SF_BLK_MROOM set.

This unify HTTP/3 headers/data/trailers encoding functions. Negative
error codes are limited to fatal error which should cause a connection
closure. Not enough output buffer space is only a transient condition
which is reflect by the QC_SF_BLK_MROOM flag.

diff --git a/src/h3.c b/src/h3.c
index 5b9d85d622f4b95f30772c6e305745abc8e46593..ff91443caa6f253104d14d74f1914a02c6df2872 100644 (file)
--- a/src/h3.c
+++ b/src/h3.c
@@ -1631,7 +1631,8 @@ static int h3_resp_headers_send(struct qcs *qcs, struct htx *htx)
  * Caller is responsible to emit an empty QUIC STREAM frame to signal the end
  * of the stream.
  *
- * Returns the size of HTX blocks removed.
+ * Returns the size of HTX blocks removed. A negative error code is returned in
+ * case of a fatal error which should caused a connection closure.
  */
 static int h3_resp_trailers_send(struct qcs *qcs, struct htx *htx)
 {
@@ -1680,8 +1681,19 @@ static int h3_resp_trailers_send(struct qcs *qcs, struct htx *htx)
                 * frame. Mux will send an empty QUIC STREAM frame with FIN.
                 */
                TRACE_DATA("skipping trailer", H3_EV_TX_FRAME|H3_EV_TX_HDR, qcs->qcc->conn, qcs);
+
+               /* Truncate UNUSED / EOT HTX blocks. */
+               blk = htx_get_head_blk(htx);
+               while (blk) {
+                       type = htx_get_blk_type(blk);
+                       ret += htx_get_blksz(blk);
+                       blk = htx_remove_blk(htx, blk);
+                       if (type == HTX_BLK_EOT)
+                               break;
+               }
                goto end;
        }
+
        list[hdr].n = ist("");
 
        if (!(res = qcc_get_stream_txbuf(qcs))) {
@@ -1692,8 +1704,9 @@ static int h3_resp_trailers_send(struct qcs *qcs, struct htx *htx)
 
        /* At least 9 bytes to store frame type + length as a varint max size */
        if (b_room(res) < 9) {
+               TRACE_STATE("not enough room for trailers frame", H3_EV_TX_FRAME|H3_EV_TX_HDR, qcs->qcc->conn, qcs);
                qcs->flags |= QC_SF_BLK_MROOM;
-               goto err;
+               goto end;
        }
 
        /* Force buffer realignment as size required to encode headers is unknown. */
@@ -1703,8 +1716,9 @@ static int h3_resp_trailers_send(struct qcs *qcs, struct htx *htx)
        headers_buf = b_make(b_peek(res, b_data(res) + 9), b_contig_space(res) - 9, 0, 0);
 
        if (qpack_encode_field_section_line(&headers_buf)) {
+               TRACE_STATE("not enough room for trailers section line", H3_EV_TX_FRAME|H3_EV_TX_HDR, qcs->qcc->conn, qcs);
                qcs->flags |= QC_SF_BLK_MROOM;
-               goto err;
+               goto end;
        }
 
        tail = b_tail(&headers_buf);
@@ -1724,8 +1738,9 @@ static int h3_resp_trailers_send(struct qcs *qcs, struct htx *htx)
                }
 
                if (qpack_encode_header(&headers_buf, list[hdr].n, list[hdr].v)) {
+                       TRACE_STATE("not enough room for all trailers", H3_EV_TX_FRAME|H3_EV_TX_HDR, qcs->qcc->conn, qcs);
                        qcs->flags |= QC_SF_BLK_MROOM;
-                       goto err;
+                       goto end;
                }
        }
 
@@ -1735,21 +1750,20 @@ static int h3_resp_trailers_send(struct qcs *qcs, struct htx *htx)
                 * frame. Mux will send an empty QUIC STREAM frame with FIN.
                 */
                TRACE_DATA("skipping trailer", H3_EV_TX_FRAME|H3_EV_TX_HDR, qcs->qcc->conn, qcs);
-               goto end;
+       }
+       else {
+               /* Now that all headers are encoded, we are certain that res
+                * buffer is big enough.
+                */
+               TRACE_DATA("encoding TRAILERS frame", H3_EV_TX_FRAME|H3_EV_TX_HDR,
+                          qcs->qcc->conn, qcs);
+               b_putchr(res, 0x01); /* h3 HEADERS frame type */
+               if (!b_quic_enc_int(res, b_data(&headers_buf), 8))
+                       ABORT_NOW();
+               b_add(res, b_data(&headers_buf));
        }
 
-       /* Now that all headers are encoded, we are certain that res buffer is
-        * big enough.
-        */
-       TRACE_DATA("encoding TRAILERS frame", H3_EV_TX_FRAME|H3_EV_TX_HDR,
-                  qcs->qcc->conn, qcs);
-       b_putchr(res, 0x01); /* h3 HEADERS frame type */
-       if (!b_quic_enc_int(res, b_data(&headers_buf), 8))
-               ABORT_NOW();
-       b_add(res, b_data(&headers_buf));
-
- end:
-       ret = 0;
+       /* Encoding success, truncate HTX blocks until EOT. */
        blk = htx_get_head_blk(htx);
        while (blk) {
                type = htx_get_blk_type(blk);
@@ -1759,6 +1773,7 @@ static int h3_resp_trailers_send(struct qcs *qcs, struct htx *htx)
                        break;
        }
 
+ end:
        TRACE_LEAVE(H3_EV_TX_FRAME|H3_EV_TX_HDR, qcs->qcc->conn, qcs);
        return ret;
 
@@ -1962,10 +1977,8 @@ static size_t h3_snd_buf(struct qcs *qcs, struct buffer *buf, size_t count)
                        break;
                }
 
-               /* If an error occurred, either buffer space or connection error
-                * must be set to break current loop.
-                */
-               BUG_ON(ret < 0 && !(qcs->flags & QC_SF_BLK_MROOM) && !h3c->err);
+               /* If an error occured, connection error must be set to break from the current loop. */
+               BUG_ON(ret < 0 && !h3c->err);
        }
 
        /* Interrupt sending on connection error. */