MINOR: h3: use smallbuf for request header emission

Similarly to HTTP/3 response encoding, a small buffer is first allocated
for the request encoding on the backend side. If this is not sufficient,
the smallbuf is replaced by a standard buffer and encoding is restarted.

This is useful to reduce the window usage over a connection of smaller
requests.

diff --git a/src/h3.c b/src/h3.c
index 91cf6b6472bf825362909b091eae609f170d7da8..65bcddc26fed74ac49ebb8caa7119addfea116e9 100644 (file)
--- a/src/h3.c
+++ b/src/h3.c
@@ -2011,6 +2011,7 @@ static int h3_req_headers_send(struct qcs *qcs, struct htx *htx)
        struct htx_sl *sl;
        struct ist meth, uri, scheme = IST_NULL, auth = IST_NULL;
        int frame_length_size;  /* size in bytes of frame length varint field */
+       int smallbuf = 1;
        int ret, err, hdr;
 
        hdr = 0;
@@ -2051,19 +2052,27 @@ static int h3_req_headers_send(struct qcs *qcs, struct htx *htx)
        /* marker for end of headers */
        list[hdr].n = ist("");
 
-       res = qcc_get_stream_txbuf(qcs, &err, 0);
-       BUG_ON(!res);
+ retry:
+       res = smallbuf ? qcc_get_stream_txbuf(qcs, &err, 1) :
+                        qcc_realloc_stream_txbuf(qcs);
+       if (!res) {
+               if (err)
+                       goto err;
+
+               goto end;
+       }
+
+       if (unlikely(b_contig_space(res) < 5))
+               goto err_full;
 
-       b_reset(&outbuf);
-       outbuf = b_make(b_tail(res), b_contig_space(res), 0, 0);
        /* Start the headers after frame type + length */
-       headers_buf = b_make(b_head(res) + 5, b_size(res) - 5, 0, 0);
+       headers_buf = b_make(b_tail(res) + 5, b_contig_space(res) - 5, 0, 0);
 
        if (qpack_encode_field_section_line(&headers_buf))
-               goto err;
+               goto err_full;
 
        if (qpack_encode_method(&headers_buf, sl->info.req.meth, meth))
-               goto err;
+               goto err_full;
 
        if (uri.ptr[0] != '/' && uri.ptr[0] != '*') {
                int len = 1;
@@ -2094,14 +2103,14 @@ static int h3_req_headers_send(struct qcs *qcs, struct htx *htx)
        }
 
        if (qpack_encode_scheme(&headers_buf, scheme))
-               goto err;
+               goto err_full;
 
        if (qpack_encode_path(&headers_buf, uri))
-               goto err;
+               goto err_full;
 
        if (istlen(auth)) {
                if (qpack_encode_auth(&headers_buf, auth))
-                       goto err;
+                       goto err_full;
        }
 
        /* Encode every parsed headers, stop at empty one. */
@@ -2138,7 +2147,7 @@ static int h3_req_headers_send(struct qcs *qcs, struct htx *htx)
                        continue;
 
                if (h3_encode_header(&headers_buf, list[hdr].n, list[hdr].v))
-                       goto err;
+                       goto err_full;
        }
 
        /* Now that all headers are encoded, we are certain that res buffer is
@@ -2160,8 +2169,14 @@ static int h3_req_headers_send(struct qcs *qcs, struct htx *htx)
                        break;
        }
 
+ end:
        return ret;
 
+ err_full:
+       if (smallbuf) {
+               smallbuf = 0;
+               goto retry;
+       }
  err:
        return -1;
 }