MEDIUM: mux-h2: replace all occurrences of mbuf with a buffer ring

For now it's only one buffer long so the head and tails are always the
same, thus it doesn't change what used to work. In short, br_tail(h2c->mbuf)
was inserted everywhere we used to have h2c->mbuf.

diff --git a/src/mux_h2.c b/src/mux_h2.c
index 8c696bf68800dcb6f958d1fffa9c0c594ec746db..7e9ba043d5d12e398e19ba603e0c7ab241f413bb 100644 (file)
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -78,6 +78,10 @@ enum h2_cs {
        H2_CS_ENTRIES    // must be last
 } __attribute__((packed));
 
+
+/* 2 buffers: one for the ring's root, one for the mbuf itself */
+#define H2C_MBUF_CNT 2
+
 /* H2 connection descriptor */
 struct h2c {
        struct connection *conn;
@@ -105,7 +109,7 @@ struct h2c {
        int32_t last_sid; /* last processed stream ID for GOAWAY, <0 before preface */
 
        /* states for the mux direction */
-       struct buffer mbuf;    /* mux buffer */
+       struct buffer mbuf[H2C_MBUF_CNT];   /* mux buffers (ring) */
        int32_t msi; /* mux stream ID (<0 = idle) */
        int32_t mfl; /* mux frame length (if dsi >= 0) */
        int8_t  mft; /* mux frame type   (if dsi >= 0) */
@@ -306,13 +310,12 @@ h2c_is_dead(struct h2c *h2c)
            ((h2c->conn->flags & CO_FL_ERROR) ||    /* errors close immediately */
             (h2c->st0 >= H2_CS_ERROR && !h2c->task) || /* a timeout stroke earlier */
             (!(h2c->conn->owner)) || /* Nobody's left to take care of the connection, drop it now */
-            (!b_data(&h2c->mbuf) &&  /* mux buffer empty, also process clean events below */
+            (!b_data(br_tail(h2c->mbuf)) &&  /* mux buffer empty, also process clean events below */
              (conn_xprt_read0_pending(h2c->conn) ||
               (h2c->last_sid >= 0 && h2c->max_id >= h2c->last_sid)))))
                return 1;
 
        return 0;
-
 }
 
 /*****************************************************/
@@ -384,7 +387,7 @@ static int h2_buf_available(void *target)
                return 1;
        }
 
-       if ((h2c->flags & H2_CF_MUX_MALLOC) && b_alloc_margin(&h2c->mbuf, 0)) {
+       if ((h2c->flags & H2_CF_MUX_MALLOC) && b_alloc_margin(br_tail(h2c->mbuf), 0)) {
                h2c->flags &= ~H2_CF_MUX_MALLOC;
 
                if (h2c->flags & H2_CF_DEM_MROOM) {
@@ -560,7 +563,7 @@ static int h2_init(struct connection *conn, struct proxy *prx, struct session *s
 
        h2c->last_sid = -1;
 
-       h2c->mbuf = BUF_NULL;
+       br_init(h2c->mbuf, sizeof(h2c->mbuf) / sizeof(h2c->mbuf[0]));
        h2c->miw = 65535; /* mux initial window size */
        h2c->mws = 65535; /* mux window size */
        h2c->mfs = 16384; /* initial max frame size */
@@ -651,7 +654,7 @@ static void h2_release(struct h2c *h2c)
                HA_SPIN_UNLOCK(BUF_WQ_LOCK, &buffer_wq_lock);
 
                h2_release_buf(h2c, &h2c->dbuf);
-               h2_release_buf(h2c, &h2c->mbuf);
+               h2_release_buf(h2c, br_tail(h2c->mbuf));
 
                if (h2c->task) {
                        h2c->task->context = NULL;
@@ -1061,7 +1064,7 @@ static int h2c_send_settings(struct h2c *h2c)
                return 0;
        }
 
-       res = h2_get_buf(h2c, &h2c->mbuf);
+       res = h2_get_buf(h2c, br_tail(h2c->mbuf));
        if (!res) {
                h2c->flags |= H2_CF_MUX_MALLOC;
                h2c->flags |= H2_CF_DEM_MROOM;
@@ -1178,7 +1181,7 @@ static int h2c_bck_send_preface(struct h2c *h2c)
                return 0;
        }
 
-       res = h2_get_buf(h2c, &h2c->mbuf);
+       res = h2_get_buf(h2c, br_tail(h2c->mbuf));
        if (!res) {
                h2c->flags |= H2_CF_MUX_MALLOC;
                h2c->flags |= H2_CF_DEM_MROOM;
@@ -1219,7 +1222,7 @@ static int h2c_send_goaway_error(struct h2c *h2c, struct h2s *h2s)
                return 0;
        }
 
-       res = h2_get_buf(h2c, &h2c->mbuf);
+       res = h2_get_buf(h2c, br_tail(h2c->mbuf));
        if (!res) {
                h2c->flags |= H2_CF_MUX_MALLOC;
                if (h2s)
@@ -1291,7 +1294,7 @@ static int h2s_send_rst_stream(struct h2c *h2c, struct h2s *h2s)
                return 0;
        }
 
-       res = h2_get_buf(h2c, &h2c->mbuf);
+       res = h2_get_buf(h2c, br_tail(h2c->mbuf));
        if (!res) {
                h2c->flags |= H2_CF_MUX_MALLOC;
                h2s->flags |= H2_SF_BLK_MROOM;
@@ -1351,7 +1354,7 @@ static int h2c_send_rst_stream(struct h2c *h2c, struct h2s *h2s)
                return 0;
        }
 
-       res = h2_get_buf(h2c, &h2c->mbuf);
+       res = h2_get_buf(h2c, br_tail(h2c->mbuf));
        if (!res) {
                h2c->flags |= H2_CF_MUX_MALLOC;
                h2c->flags |= H2_CF_DEM_MROOM;
@@ -1407,7 +1410,7 @@ static int h2_send_empty_data_es(struct h2s *h2s)
                return 0;
        }
 
-       res = h2_get_buf(h2c, &h2c->mbuf);
+       res = h2_get_buf(h2c, br_tail(h2c->mbuf));
        if (!res) {
                h2c->flags |= H2_CF_MUX_MALLOC;
                h2s->flags |= H2_SF_BLK_MROOM;
@@ -1607,7 +1610,7 @@ static int h2c_ack_settings(struct h2c *h2c)
                return 0;
        }
 
-       res = h2_get_buf(h2c, &h2c->mbuf);
+       res = h2_get_buf(h2c, br_tail(h2c->mbuf));
        if (!res) {
                h2c->flags |= H2_CF_MUX_MALLOC;
                h2c->flags |= H2_CF_DEM_MROOM;
@@ -1662,7 +1665,7 @@ static int h2c_send_window_update(struct h2c *h2c, int sid, uint32_t increment)
                return 0;
        }
 
-       res = h2_get_buf(h2c, &h2c->mbuf);
+       res = h2_get_buf(h2c, br_tail(h2c->mbuf));
        if (!res) {
                h2c->flags |= H2_CF_MUX_MALLOC;
                h2c->flags |= H2_CF_DEM_MROOM;
@@ -1753,7 +1756,7 @@ static int h2c_ack_ping(struct h2c *h2c)
                return 0;
        }
 
-       res = h2_get_buf(h2c, &h2c->mbuf);
+       res = h2_get_buf(h2c, br_tail(h2c->mbuf));
        if (!res) {
                h2c->flags |= H2_CF_MUX_MALLOC;
                h2c->flags |= H2_CF_DEM_MROOM;
@@ -2772,13 +2775,13 @@ static int h2_send(struct h2c *h2c)
                if (h2c->flags & (H2_CF_MUX_MFULL | H2_CF_DEM_MBUSY | H2_CF_DEM_MROOM))
                        flags |= CO_SFL_MSG_MORE;
 
-               if (b_data(&h2c->mbuf)) {
-                       int ret = conn->xprt->snd_buf(conn, conn->xprt_ctx, &h2c->mbuf, b_data(&h2c->mbuf), flags);
+               if (b_data(br_tail(h2c->mbuf))) {
+                       int ret = conn->xprt->snd_buf(conn, conn->xprt_ctx, br_tail(h2c->mbuf), b_data(br_tail(h2c->mbuf)), flags);
                        if (!ret)
                                break;
                        sent = 1;
-                       b_del(&h2c->mbuf, ret);
-                       b_realign_if_empty(&h2c->mbuf);
+                       b_del(br_tail(h2c->mbuf), ret);
+                       b_realign_if_empty(br_tail(h2c->mbuf));
                }
 
                /* wrote at least one byte, the buffer is not full anymore */
@@ -2787,7 +2790,7 @@ static int h2_send(struct h2c *h2c)
 
        if (conn->flags & CO_FL_SOCK_WR_SH) {
                /* output closed, nothing to send, clear the buffer to release it */
-               b_reset(&h2c->mbuf);
+               b_reset(br_tail(h2c->mbuf));
        }
        /* We're not full anymore, so we can wake any task that are waiting
         * for us.
@@ -2816,7 +2819,7 @@ static int h2_send(struct h2c *h2c)
                }
        }
        /* We're done, no more to send */
-       if (!b_data(&h2c->mbuf))
+       if (!b_data(br_tail(h2c->mbuf)))
                return sent;
 schedule:
        if (!(h2c->wait_event.events & SUB_RETRY_SEND))
@@ -2909,13 +2912,13 @@ static int h2_process(struct h2c *h2c)
        if ((conn->flags & CO_FL_SOCK_WR_SH) ||
            h2c->st0 == H2_CS_ERROR2 || (h2c->flags & H2_CF_GOAWAY_FAILED) ||
            (h2c->st0 != H2_CS_ERROR &&
-            !b_data(&h2c->mbuf) &&
+            !b_data(br_tail(h2c->mbuf)) &&
             (h2c->mws <= 0 || LIST_ISEMPTY(&h2c->fctl_list)) &&
             ((h2c->flags & H2_CF_MUX_BLOCK_ANY) || LIST_ISEMPTY(&h2c->send_list))))
-               h2_release_buf(h2c, &h2c->mbuf);
+               h2_release_buf(h2c, br_tail(h2c->mbuf));
 
        if (h2c->task) {
-               if (eb_is_empty(&h2c->streams_by_id) || b_data(&h2c->mbuf)) {
+               if (eb_is_empty(&h2c->streams_by_id) || b_data(br_tail(h2c->mbuf))) {
                        h2c->task->expire = tick_add(now_ms, h2c->last_sid < 0 ? h2c->timeout : h2c->shut_timeout);
                        task_queue(h2c->task);
                }
@@ -2960,7 +2963,7 @@ static struct task *h2_timeout_task(struct task *t, void *context, unsigned shor
        h2c_error(h2c, H2_ERR_NO_ERROR);
        h2_wake_some_streams(h2c, 0);
 
-       if (b_data(&h2c->mbuf)) {
+       if (b_data(br_tail(h2c->mbuf))) {
                /* don't even try to send a GOAWAY, the buffer is stuck */
                h2c->flags |= H2_CF_GOAWAY_FAILED;
        }
@@ -2970,11 +2973,11 @@ static struct task *h2_timeout_task(struct task *t, void *context, unsigned shor
        if (h2c_send_goaway_error(h2c, NULL) <= 0)
                h2c->flags |= H2_CF_GOAWAY_FAILED;
 
-       if (b_data(&h2c->mbuf) && !(h2c->flags & H2_CF_GOAWAY_FAILED) && conn_xprt_ready(h2c->conn)) {
-               int ret = h2c->conn->xprt->snd_buf(h2c->conn, h2c->conn->xprt_ctx, &h2c->mbuf, b_data(&h2c->mbuf), 0);
+       if (b_data(br_tail(h2c->mbuf)) && !(h2c->flags & H2_CF_GOAWAY_FAILED) && conn_xprt_ready(h2c->conn)) {
+               int ret = h2c->conn->xprt->snd_buf(h2c->conn, h2c->conn->xprt_ctx, br_tail(h2c->mbuf), b_data(br_tail(h2c->mbuf)), 0);
                if (ret > 0) {
-                       b_del(&h2c->mbuf, ret);
-                       b_realign_if_empty(&h2c->mbuf);
+                       b_del(br_tail(h2c->mbuf), ret);
+                       b_realign_if_empty(br_tail(h2c->mbuf));
                }
        }
 
@@ -3157,7 +3160,7 @@ static void h2_detach(struct conn_stream *cs)
                h2_release(h2c);
        }
        else if (h2c->task) {
-               if (eb_is_empty(&h2c->streams_by_id) || b_data(&h2c->mbuf)) {
+               if (eb_is_empty(&h2c->streams_by_id) || b_data(br_tail(h2c->mbuf))) {
                        h2c->task->expire = tick_add(now_ms, h2c->last_sid < 0 ? h2c->timeout : h2c->shut_timeout);
                        task_queue(h2c->task);
                }
@@ -3888,7 +3891,7 @@ static size_t h2s_frt_make_resp_headers(struct h2s *h2s, const struct buffer *bu
                return 0;
        }
 
-       if (!h2_get_buf(h2c, &h2c->mbuf)) {
+       if (!h2_get_buf(h2c, br_tail(h2c->mbuf))) {
                h2c->flags |= H2_CF_MUX_MALLOC;
                h2s->flags |= H2_SF_BLK_MROOM;
                return 0;
@@ -3934,14 +3937,14 @@ static size_t h2s_frt_make_resp_headers(struct h2s *h2s, const struct buffer *bu
        chunk_reset(&outbuf);
 
        while (1) {
-               outbuf.area  = b_tail(&h2c->mbuf);
-               outbuf.size = b_contig_space(&h2c->mbuf);
+               outbuf.area  = b_tail(br_tail(h2c->mbuf));
+               outbuf.size = b_contig_space(br_tail(h2c->mbuf));
                outbuf.data = 0;
 
-               if (outbuf.size >= 9 || !b_space_wraps(&h2c->mbuf))
+               if (outbuf.size >= 9 || !b_space_wraps(br_tail(h2c->mbuf)))
                        break;
        realign_again:
-               b_slow_realign(&h2c->mbuf, trash.area, b_data(&h2c->mbuf));
+               b_slow_realign(br_tail(h2c->mbuf), trash.area, b_data(br_tail(h2c->mbuf)));
        }
 
        if (outbuf.size < 9)
@@ -3961,7 +3964,7 @@ static size_t h2s_frt_make_resp_headers(struct h2s *h2s, const struct buffer *bu
        }
 
        if (!hpack_encode_str_status(&outbuf, h2s->status, list[0].v)) {
-               if (b_space_wraps(&h2c->mbuf))
+               if (b_space_wraps(br_tail(h2c->mbuf)))
                        goto realign_again;
                goto full;
        }
@@ -3981,7 +3984,7 @@ static size_t h2s_frt_make_resp_headers(struct h2s *h2s, const struct buffer *bu
 
                if (!hpack_encode_header(&outbuf, list[hdr].n, list[hdr].v)) {
                        /* output full */
-                       if (b_space_wraps(&h2c->mbuf))
+                       if (b_space_wraps(br_tail(h2c->mbuf)))
                                goto realign_again;
                        goto full;
                }
@@ -4001,7 +4004,7 @@ static size_t h2s_frt_make_resp_headers(struct h2s *h2s, const struct buffer *bu
        max -= ret;
 
        /* commit the H2 response */
-       b_add(&h2c->mbuf, outbuf.data);
+       b_add(br_tail(h2c->mbuf), outbuf.data);
        h2s->flags |= H2_SF_HEADERS_SENT;
 
        if (es_now) {
@@ -4059,7 +4062,7 @@ static size_t h2s_frt_make_resp_data(struct h2s *h2s, const struct buffer *buf,
                goto end;
        }
 
-       if (!h2_get_buf(h2c, &h2c->mbuf)) {
+       if (!h2_get_buf(h2c, br_tail(h2c->mbuf))) {
                h2c->flags |= H2_CF_MUX_MALLOC;
                h2s->flags |= H2_SF_BLK_MROOM;
                goto end;
@@ -4072,11 +4075,11 @@ static size_t h2s_frt_make_resp_data(struct h2s *h2s, const struct buffer *buf,
        chunk_reset(&outbuf);
 
        while (1) {
-               outbuf.area  = b_tail(&h2c->mbuf);
-               outbuf.size = b_contig_space(&h2c->mbuf);
+               outbuf.area  = b_tail(br_tail(h2c->mbuf));
+               outbuf.size = b_contig_space(br_tail(h2c->mbuf));
                outbuf.data = 0;
 
-               if (outbuf.size >= 9 || !b_space_wraps(&h2c->mbuf))
+               if (outbuf.size >= 9 || !b_space_wraps(br_tail(h2c->mbuf)))
                        break;
        realign_again:
                /* If there are pending data in the output buffer, and we have
@@ -4084,13 +4087,13 @@ static size_t h2s_frt_make_resp_data(struct h2s *h2s, const struct buffer *buf,
                 * still perform a copy anyway. Otherwise we'll pretend the mbuf
                 * is full and wait, to save some slow realign calls.
                 */
-               if ((max + 9 > b_room(&h2c->mbuf) || max >= b_size(&h2c->mbuf) / 4)) {
+               if ((max + 9 > b_room(br_tail(h2c->mbuf)) || max >= b_size(br_tail(h2c->mbuf)) / 4)) {
                        h2c->flags |= H2_CF_MUX_MFULL;
                        h2s->flags |= H2_SF_BLK_MROOM;
                        goto end;
                }
 
-               b_slow_realign(&h2c->mbuf, trash.area, b_data(&h2c->mbuf));
+               b_slow_realign(br_tail(h2c->mbuf), trash.area, b_data(br_tail(h2c->mbuf)));
        }
 
        if (outbuf.size < 9) {
@@ -4191,9 +4194,9 @@ static size_t h2s_frt_make_resp_data(struct h2s *h2s, const struct buffer *buf,
                 * the amount of data to move is low, let's defragment the
                 * buffer now.
                 */
-               if (b_space_wraps(&h2c->mbuf) &&
-                   (size + 9 <= b_room(&h2c->mbuf)) &&
-                   b_data(&h2c->mbuf) <= MAX_DATA_REALIGN)
+               if (b_space_wraps(br_tail(h2c->mbuf)) &&
+                   (size + 9 <= b_room(br_tail(h2c->mbuf))) &&
+                   b_data(br_tail(h2c->mbuf)) <= MAX_DATA_REALIGN)
                        goto realign_again;
                size = outbuf.size - 9;
        }
@@ -4266,7 +4269,7 @@ static size_t h2s_frt_make_resp_data(struct h2s *h2s, const struct buffer *buf,
                outbuf.area[4] |= H2_F_DATA_END_STREAM;
 
        /* commit the H2 response */
-       b_add(&h2c->mbuf, size + 9);
+       b_add(br_tail(h2c->mbuf), size + 9);
 
        /* consume incoming H1 response */
        if (size > 0) {
@@ -4334,7 +4337,7 @@ static size_t h2s_htx_frt_make_resp_headers(struct h2s *h2s, struct htx *htx)
                return 0;
        }
 
-       if (!h2_get_buf(h2c, &h2c->mbuf)) {
+       if (!h2_get_buf(h2c, br_tail(h2c->mbuf))) {
                h2c->flags |= H2_CF_MUX_MALLOC;
                h2s->flags |= H2_SF_BLK_MROOM;
                return 0;
@@ -4395,14 +4398,14 @@ static size_t h2s_htx_frt_make_resp_headers(struct h2s *h2s, struct htx *htx)
        chunk_reset(&outbuf);
 
        while (1) {
-               outbuf.area  = b_tail(&h2c->mbuf);
-               outbuf.size = b_contig_space(&h2c->mbuf);
+               outbuf.area  = b_tail(br_tail(h2c->mbuf));
+               outbuf.size = b_contig_space(br_tail(h2c->mbuf));
                outbuf.data = 0;
 
-               if (outbuf.size >= 9 || !b_space_wraps(&h2c->mbuf))
+               if (outbuf.size >= 9 || !b_space_wraps(br_tail(h2c->mbuf)))
                        break;
        realign_again:
-               b_slow_realign(&h2c->mbuf, trash.area, b_data(&h2c->mbuf));
+               b_slow_realign(br_tail(h2c->mbuf), trash.area, b_data(br_tail(h2c->mbuf)));
        }
 
        if (outbuf.size < 9)
@@ -4415,7 +4418,7 @@ static size_t h2s_htx_frt_make_resp_headers(struct h2s *h2s, struct htx *htx)
 
        /* encode status, which necessarily is the first one */
        if (!hpack_encode_int_status(&outbuf, h2s->status)) {
-               if (b_space_wraps(&h2c->mbuf))
+               if (b_space_wraps(br_tail(h2c->mbuf)))
                        goto realign_again;
                goto full;
        }
@@ -4435,7 +4438,7 @@ static size_t h2s_htx_frt_make_resp_headers(struct h2s *h2s, struct htx *htx)
 
                if (!hpack_encode_header(&outbuf, list[hdr].n, list[hdr].v)) {
                        /* output full */
-                       if (b_space_wraps(&h2c->mbuf))
+                       if (b_space_wraps(br_tail(h2c->mbuf)))
                                goto realign_again;
                        goto full;
                }
@@ -4459,7 +4462,7 @@ static size_t h2s_htx_frt_make_resp_headers(struct h2s *h2s, struct htx *htx)
                outbuf.area[4] |= H2_F_HEADERS_END_STREAM;
 
        /* commit the H2 response */
-       b_add(&h2c->mbuf, outbuf.data);
+       b_add(br_tail(h2c->mbuf), outbuf.data);
 
        /* indicates the HEADERS frame was sent, except for 1xx responses. For
         * 1xx responses, another HEADERS frame is expected.
@@ -4539,7 +4542,7 @@ static size_t h2s_htx_bck_make_req_headers(struct h2s *h2s, struct htx *htx)
                return 0;
        }
 
-       if (!h2_get_buf(h2c, &h2c->mbuf)) {
+       if (!h2_get_buf(h2c, br_tail(h2c->mbuf))) {
                h2c->flags |= H2_CF_MUX_MALLOC;
                h2s->flags |= H2_SF_BLK_MROOM;
                return 0;
@@ -4594,14 +4597,14 @@ static size_t h2s_htx_bck_make_req_headers(struct h2s *h2s, struct htx *htx)
        chunk_reset(&outbuf);
 
        while (1) {
-               outbuf.area  = b_tail(&h2c->mbuf);
-               outbuf.size = b_contig_space(&h2c->mbuf);
+               outbuf.area  = b_tail(br_tail(h2c->mbuf));
+               outbuf.size = b_contig_space(br_tail(h2c->mbuf));
                outbuf.data = 0;
 
-               if (outbuf.size >= 9 || !b_space_wraps(&h2c->mbuf))
+               if (outbuf.size >= 9 || !b_space_wraps(br_tail(h2c->mbuf)))
                        break;
        realign_again:
-               b_slow_realign(&h2c->mbuf, trash.area, b_data(&h2c->mbuf));
+               b_slow_realign(br_tail(h2c->mbuf), trash.area, b_data(br_tail(h2c->mbuf)));
        }
 
        if (outbuf.size < 9)
@@ -4614,7 +4617,7 @@ static size_t h2s_htx_bck_make_req_headers(struct h2s *h2s, struct htx *htx)
 
        /* encode the method, which necessarily is the first one */
        if (!hpack_encode_method(&outbuf, sl->info.req.meth, meth)) {
-               if (b_space_wraps(&h2c->mbuf))
+               if (b_space_wraps(br_tail(h2c->mbuf)))
                        goto realign_again;
                goto full;
        }
@@ -4628,7 +4631,7 @@ static size_t h2s_htx_bck_make_req_headers(struct h2s *h2s, struct htx *htx)
                /* encode the scheme which is always "https" (or 0x86 for "http") */
                if (!hpack_encode_scheme(&outbuf, ist("https"))) {
                        /* output full */
-                       if (b_space_wraps(&h2c->mbuf))
+                       if (b_space_wraps(br_tail(h2c->mbuf)))
                                goto realign_again;
                        goto full;
                }
@@ -4636,7 +4639,7 @@ static size_t h2s_htx_bck_make_req_headers(struct h2s *h2s, struct htx *htx)
                /* encode the path, which necessarily is the second one */
                if (!hpack_encode_path(&outbuf, path)) {
                        /* output full */
-                       if (b_space_wraps(&h2c->mbuf))
+                       if (b_space_wraps(br_tail(h2c->mbuf)))
                                goto realign_again;
                        goto full;
                }
@@ -4660,7 +4663,7 @@ static size_t h2s_htx_bck_make_req_headers(struct h2s *h2s, struct htx *htx)
 
        if (auth.ptr && !hpack_encode_header(&outbuf, ist(":authority"), auth)) {
                /* output full */
-               if (b_space_wraps(&h2c->mbuf))
+               if (b_space_wraps(br_tail(h2c->mbuf)))
                        goto realign_again;
                goto full;
        }
@@ -4681,7 +4684,7 @@ static size_t h2s_htx_bck_make_req_headers(struct h2s *h2s, struct htx *htx)
 
                if (!hpack_encode_header(&outbuf, list[hdr].n, list[hdr].v)) {
                        /* output full */
-                       if (b_space_wraps(&h2c->mbuf))
+                       if (b_space_wraps(br_tail(h2c->mbuf)))
                                goto realign_again;
                        goto full;
                }
@@ -4709,7 +4712,7 @@ static size_t h2s_htx_bck_make_req_headers(struct h2s *h2s, struct htx *htx)
                outbuf.area[4] |= H2_F_HEADERS_END_STREAM;
 
        /* commit the H2 response */
-       b_add(&h2c->mbuf, outbuf.data);
+       b_add(br_tail(h2c->mbuf), outbuf.data);
        h2s->flags |= H2_SF_HEADERS_SENT;
        h2s->st = H2_SS_OPEN;
 
@@ -4777,7 +4780,7 @@ static size_t h2s_htx_frt_make_resp_data(struct h2s *h2s, struct buffer *buf, si
                goto end;
        }
 
-       if (!h2_get_buf(h2c, &h2c->mbuf)) {
+       if (!h2_get_buf(h2c, br_tail(h2c->mbuf))) {
                h2c->flags |= H2_CF_MUX_MALLOC;
                h2s->flags |= H2_SF_BLK_MROOM;
                goto end;
@@ -4842,18 +4845,18 @@ static size_t h2s_htx_frt_make_resp_data(struct h2s *h2s, struct buffer *buf, si
        if (unlikely(fsize == count &&
                     htx->used == 1 && type == HTX_BLK_DATA &&
                     fsize <= h2s->mws && fsize <= h2c->mws && fsize <= h2c->mfs)) {
-               void *old_area = h2c->mbuf.area;
+               void *old_area = br_tail(h2c->mbuf)->area;
 
-               if (b_data(&h2c->mbuf)) {
+               if (b_data(br_tail(h2c->mbuf))) {
                        /* Too bad there are data left there. We're willing to memcpy/memmove
                         * up to 1/4 of the buffer, which means that it's OK to copy a large
                         * frame into a buffer containing few data if it needs to be realigned,
                         * and that it's also OK to copy few data without realigning. Otherwise
                         * we'll pretend the mbuf is full and wait for it to become empty.
                         */
-                       if (fsize + 9 <= b_room(&h2c->mbuf) &&
-                           (b_data(&h2c->mbuf) <= b_size(&h2c->mbuf) / 4 ||
-                            (fsize <= b_size(&h2c->mbuf) / 4 && fsize + 9 <= b_contig_space(&h2c->mbuf))))
+                       if (fsize + 9 <= b_room(br_tail(h2c->mbuf)) &&
+                           (b_data(br_tail(h2c->mbuf)) <= b_size(br_tail(h2c->mbuf)) / 4 ||
+                            (fsize <= b_size(br_tail(h2c->mbuf)) / 4 && fsize + 9 <= b_contig_space(br_tail(h2c->mbuf)))))
                                goto copy;
 
                        h2c->flags |= H2_CF_MUX_MFULL;
@@ -4864,10 +4867,10 @@ static size_t h2s_htx_frt_make_resp_data(struct h2s *h2s, struct buffer *buf, si
                /* map an H2 frame to the HTX block so that we can put the
                 * frame header there.
                 */
-               h2c->mbuf.area = buf->area;
-               h2c->mbuf.head = sizeof(struct htx) + blk->addr - 9;
-               h2c->mbuf.data = fsize + 9;
-               outbuf.area    = b_head(&h2c->mbuf);
+               br_tail(h2c->mbuf)->area = buf->area;
+               br_tail(h2c->mbuf)->head = sizeof(struct htx) + blk->addr - 9;
+               br_tail(h2c->mbuf)->data = fsize + 9;
+               outbuf.area    = b_head(br_tail(h2c->mbuf));
 
                /* prepend an H2 DATA frame header just before the DATA block */
                memcpy(outbuf.area, "\x00\x00\x00\x00\x00", 5);
@@ -4889,14 +4892,14 @@ static size_t h2s_htx_frt_make_resp_data(struct h2s *h2s, struct buffer *buf, si
        /* for DATA and EOM we'll have to emit a frame, even if empty */
 
        while (1) {
-               outbuf.area  = b_tail(&h2c->mbuf);
-               outbuf.size = b_contig_space(&h2c->mbuf);
+               outbuf.area  = b_tail(br_tail(h2c->mbuf));
+               outbuf.size = b_contig_space(br_tail(h2c->mbuf));
                outbuf.data = 0;
 
-               if (outbuf.size >= 9 || !b_space_wraps(&h2c->mbuf))
+               if (outbuf.size >= 9 || !b_space_wraps(br_tail(h2c->mbuf)))
                        break;
        realign_again:
-               b_slow_realign(&h2c->mbuf, trash.area, b_data(&h2c->mbuf));
+               b_slow_realign(br_tail(h2c->mbuf), trash.area, b_data(br_tail(h2c->mbuf)));
        }
 
        if (outbuf.size < 9) {
@@ -4949,9 +4952,9 @@ static size_t h2s_htx_frt_make_resp_data(struct h2s *h2s, struct buffer *buf, si
                 * the amount of data to move is low, let's defragment the
                 * buffer now.
                 */
-               if (b_space_wraps(&h2c->mbuf) &&
-                   (fsize + 9 <= b_room(&h2c->mbuf)) &&
-                   b_data(&h2c->mbuf) <= MAX_DATA_REALIGN)
+               if (b_space_wraps(br_tail(h2c->mbuf)) &&
+                   (fsize + 9 <= b_room(br_tail(h2c->mbuf))) &&
+                   b_data(br_tail(h2c->mbuf)) <= MAX_DATA_REALIGN)
                        goto realign_again;
                fsize = outbuf.size - 9;
 
@@ -4994,7 +4997,7 @@ static size_t h2s_htx_frt_make_resp_data(struct h2s *h2s, struct buffer *buf, si
                outbuf.area[4] |= H2_F_DATA_END_STREAM;
 
        /* commit the H2 response */
-       b_add(&h2c->mbuf, fsize + 9);
+       b_add(br_tail(h2c->mbuf), fsize + 9);
 
        /* consume incoming HTX block, including EOM */
        total += fsize;
@@ -5049,7 +5052,7 @@ static size_t h2s_htx_make_trailers(struct h2s *h2s, struct htx *htx)
                goto end;
        }
 
-       if (!h2_get_buf(h2c, &h2c->mbuf)) {
+       if (!h2_get_buf(h2c, br_tail(h2c->mbuf))) {
                h2c->flags |= H2_CF_MUX_MALLOC;
                h2s->flags |= H2_SF_BLK_MROOM;
                goto end;
@@ -5107,14 +5110,14 @@ static size_t h2s_htx_make_trailers(struct h2s *h2s, struct htx *htx)
        chunk_reset(&outbuf);
 
        while (1) {
-               outbuf.area  = b_tail(&h2c->mbuf);
-               outbuf.size = b_contig_space(&h2c->mbuf);
+               outbuf.area  = b_tail(br_tail(h2c->mbuf));
+               outbuf.size = b_contig_space(br_tail(h2c->mbuf));
                outbuf.data = 0;
 
-               if (outbuf.size >= 9 || !b_space_wraps(&h2c->mbuf))
+               if (outbuf.size >= 9 || !b_space_wraps(br_tail(h2c->mbuf)))
                        break;
        realign_again:
-               b_slow_realign(&h2c->mbuf, trash.area, b_data(&h2c->mbuf));
+               b_slow_realign(br_tail(h2c->mbuf), trash.area, b_data(br_tail(h2c->mbuf)));
        }
 
        if (outbuf.size < 9)
@@ -5142,7 +5145,7 @@ static size_t h2s_htx_make_trailers(struct h2s *h2s, struct htx *htx)
 
                if (!hpack_encode_header(&outbuf, list[idx].n, list[idx].v)) {
                        /* output full */
-                       if (b_space_wraps(&h2c->mbuf))
+                       if (b_space_wraps(br_tail(h2c->mbuf)))
                                goto realign_again;
                        goto full;
                }
@@ -5163,7 +5166,7 @@ static size_t h2s_htx_make_trailers(struct h2s *h2s, struct htx *htx)
        h2_set_frame_size(outbuf.area, outbuf.data - 9);
 
        /* commit the H2 response */
-       b_add(&h2c->mbuf, outbuf.data);
+       b_add(br_tail(h2c->mbuf), outbuf.data);
        h2s->flags |= H2_SF_ES_SENT;
 
        if (h2s->st == H2_SS_OPEN)
@@ -5618,8 +5621,8 @@ static void h2_show_fd(struct buffer *msg, struct connection *conn)
                      (unsigned int)b_data(&h2c->dbuf), b_orig(&h2c->dbuf),
                      (unsigned int)b_head_ofs(&h2c->dbuf), (unsigned int)b_size(&h2c->dbuf),
                      h2c->msi,
-                     (unsigned int)b_data(&h2c->mbuf), b_orig(&h2c->mbuf),
-                     (unsigned int)b_head_ofs(&h2c->mbuf), (unsigned int)b_size(&h2c->mbuf));
+                     (unsigned int)b_data(br_tail(h2c->mbuf)), b_orig(br_tail(h2c->mbuf)),
+                     (unsigned int)b_head_ofs(br_tail(h2c->mbuf)), (unsigned int)b_size(br_tail(h2c->mbuf)));
 
        if (h2s) {
                chunk_appendf(msg, " last_h2s=%p .id=%d .flg=0x%04x .rxbuf=%u@%p+%u/%u .cs=%p",