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4b7144f763
For h1 / ws, a combination of removing POLLIN wait and stashing any unused rx lets us immediately respond to rx flow control requests in a simple and effective way, because the tcp socket is the stream. But for muxed protocols like h2, that technique cannot be used because we cannot silence the whole bundle of streams because one can't handle any more rx dynamically. There are control frames and content for other streams serialized inbetween the flow controlled stream content. We have no choice but to read to so we can see the other things. Therefore for muxed protocols like h2 and spdy, rx flow control boils down to tx credit manipulation on individual streams to staunch the flow at the peer. However that requires a round trip to take effect, any transmitted packets that were in flight before the tx credit reduction arrives at the remote peer are still going to come and have to be dealt with by adding them to the stash. This patch introduces lws_buflist scatter-gather type buffer management for rxflow handling, so we can append buffer segments in a linked-list to handle whatever rx is unavoidably in flight on a stream that is trying to assert rx flow control.
70 lines
2 KiB
C
70 lines
2 KiB
C
/*
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* libwebsockets - small server side websockets and web server implementation
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*
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* Copyright (C) 2010-2018 Andy Green <andy@warmcat.com>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation:
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* version 2.1 of the License.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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* MA 02110-1301 USA
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*/
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#include <private-libwebsockets.h>
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int
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lws_handshake_client(struct lws *wsi, unsigned char **buf, size_t len)
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{
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int m;
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if ((lwsi_state(wsi) != LRS_WAITING_PROXY_REPLY) &&
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(lwsi_state(wsi) != LRS_H1C_ISSUE_HANDSHAKE) &&
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(lwsi_state(wsi) != LRS_WAITING_SERVER_REPLY) &&
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!lwsi_role_client(wsi))
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return 0;
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while (len) {
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/*
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* we were accepting input but now we stopped doing so
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*/
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if (lws_is_flowcontrolled(wsi)) {
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lwsl_debug("%s: caching %ld\n", __func__, (long)len);
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lws_rxflow_cache(wsi, *buf, 0, (int)len);
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return 0;
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}
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if (wsi->ws->rx_draining_ext) {
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#if !defined(LWS_NO_CLIENT)
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if (lwsi_role_client(wsi))
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m = lws_client_rx_sm(wsi, 0);
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else
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#endif
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m = lws_ws_rx_sm(wsi, 0);
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if (m < 0)
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return -1;
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continue;
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}
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/* account for what we're using in rxflow buffer */
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if (lws_buflist_next_segment_len(&wsi->buflist_rxflow, NULL) &&
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!lws_buflist_use_segment(&wsi->buflist_rxflow, 1))
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lws_dll_lws_remove(&wsi->dll_rxflow);
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if (lws_client_rx_sm(wsi, *(*buf)++)) {
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lwsl_debug("client_rx_sm exited\n");
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return -1;
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}
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len--;
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}
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lwsl_debug("%s: finished with %ld\n", __func__, (long)len);
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return 0;
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}
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