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view src/stream/ngx_stream_write_filter_module.c @ 9086:f68fdb017141 quic

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QUIC: optimized sending stream response. When a stream is created by client, it's often the case that nginx will send immediate response on that stream. An example is HTTP/3 request stream, which in most cases quickly replies with at least HTTP headers. QUIC stream init handlers are called from a posted event. Output QUIC frames are also sent to client from a posted event, called the push event. If the push event is posted before the stream init event, then output produced by stream may trigger sending an extra UDP datagram. To address this, push event is now re-posted when a new stream init event is posted. An example is handling 0-RTT packets. Client typically sends an init packet coalesced with a 0-RTT packet. Previously, nginx replied with a padded CRYPTO datagram, followed by a 1-RTT stream reply datagram. Now CRYPTO and STREAM packets are coalesced in one reply datagram, which saves bandwidth. Other examples include coalescing 1-RTT first stream response, and MAX_STREAMS/STREAM sent in response to ACK/STREAM.
author Roman Arutyunyan <arut@nginx.com>
date Mon, 03 Apr 2023 16:17:12 +0400
parents 32b0ba4855a6
children 9ea62b6250f2
line wrap: on
line source


/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_stream.h>


typedef struct {
    ngx_chain_t  *from_upstream;
    ngx_chain_t  *from_downstream;
} ngx_stream_write_filter_ctx_t;


static ngx_int_t ngx_stream_write_filter(ngx_stream_session_t *s,
    ngx_chain_t *in, ngx_uint_t from_upstream);
static ngx_int_t ngx_stream_write_filter_init(ngx_conf_t *cf);


static ngx_stream_module_t  ngx_stream_write_filter_module_ctx = {
    NULL,                                  /* preconfiguration */
    ngx_stream_write_filter_init,          /* postconfiguration */

    NULL,                                  /* create main configuration */
    NULL,                                  /* init main configuration */

    NULL,                                  /* create server configuration */
    NULL                                   /* merge server configuration */
};


ngx_module_t  ngx_stream_write_filter_module = {
    NGX_MODULE_V1,
    &ngx_stream_write_filter_module_ctx,   /* module context */
    NULL,                                  /* module directives */
    NGX_STREAM_MODULE,                     /* module type */
    NULL,                                  /* init master */
    NULL,                                  /* init module */
    NULL,                                  /* init process */
    NULL,                                  /* init thread */
    NULL,                                  /* exit thread */
    NULL,                                  /* exit process */
    NULL,                                  /* exit master */
    NGX_MODULE_V1_PADDING
};


static ngx_int_t
ngx_stream_write_filter(ngx_stream_session_t *s, ngx_chain_t *in,
    ngx_uint_t from_upstream)
{
    off_t                           size;
    ngx_uint_t                      last, flush, sync;
    ngx_chain_t                    *cl, *ln, **ll, **out, *chain;
    ngx_connection_t               *c;
    ngx_stream_write_filter_ctx_t  *ctx;

    ctx = ngx_stream_get_module_ctx(s, ngx_stream_write_filter_module);

    if (ctx == NULL) {
        ctx = ngx_pcalloc(s->connection->pool,
                          sizeof(ngx_stream_write_filter_ctx_t));
        if (ctx == NULL) {
            return NGX_ERROR;
        }

        ngx_stream_set_ctx(s, ctx, ngx_stream_write_filter_module);
    }

    if (from_upstream) {
        c = s->connection;
        out = &ctx->from_upstream;

    } else {
        c = s->upstream->peer.connection;
        out = &ctx->from_downstream;
    }

    if (c->error) {
        return NGX_ERROR;
    }

    size = 0;
    flush = 0;
    sync = 0;
    last = 0;
    ll = out;

    /* find the size, the flush point and the last link of the saved chain */

    for (cl = *out; cl; cl = cl->next) {
        ll = &cl->next;

        ngx_log_debug7(NGX_LOG_DEBUG_EVENT, c->log, 0,
                       "write old buf t:%d f:%d %p, pos %p, size: %z "
                       "file: %O, size: %O",
                       cl->buf->temporary, cl->buf->in_file,
                       cl->buf->start, cl->buf->pos,
                       cl->buf->last - cl->buf->pos,
                       cl->buf->file_pos,
                       cl->buf->file_last - cl->buf->file_pos);

        if (ngx_buf_size(cl->buf) == 0 && !ngx_buf_special(cl->buf)) {
            ngx_log_error(NGX_LOG_ALERT, c->log, 0,
                          "zero size buf in writer "
                          "t:%d r:%d f:%d %p %p-%p %p %O-%O",
                          cl->buf->temporary,
                          cl->buf->recycled,
                          cl->buf->in_file,
                          cl->buf->start,
                          cl->buf->pos,
                          cl->buf->last,
                          cl->buf->file,
                          cl->buf->file_pos,
                          cl->buf->file_last);

            ngx_debug_point();
            return NGX_ERROR;
        }

        if (ngx_buf_size(cl->buf) < 0) {
            ngx_log_error(NGX_LOG_ALERT, c->log, 0,
                          "negative size buf in writer "
                          "t:%d r:%d f:%d %p %p-%p %p %O-%O",
                          cl->buf->temporary,
                          cl->buf->recycled,
                          cl->buf->in_file,
                          cl->buf->start,
                          cl->buf->pos,
                          cl->buf->last,
                          cl->buf->file,
                          cl->buf->file_pos,
                          cl->buf->file_last);

            ngx_debug_point();
            return NGX_ERROR;
        }

        size += ngx_buf_size(cl->buf);

        if (cl->buf->flush || cl->buf->recycled) {
            flush = 1;
        }

        if (cl->buf->sync) {
            sync = 1;
        }

        if (cl->buf->last_buf) {
            last = 1;
        }
    }

    /* add the new chain to the existent one */

    for (ln = in; ln; ln = ln->next) {
        cl = ngx_alloc_chain_link(c->pool);
        if (cl == NULL) {
            return NGX_ERROR;
        }

        cl->buf = ln->buf;
        *ll = cl;
        ll = &cl->next;

        ngx_log_debug7(NGX_LOG_DEBUG_EVENT, c->log, 0,
                       "write new buf t:%d f:%d %p, pos %p, size: %z "
                       "file: %O, size: %O",
                       cl->buf->temporary, cl->buf->in_file,
                       cl->buf->start, cl->buf->pos,
                       cl->buf->last - cl->buf->pos,
                       cl->buf->file_pos,
                       cl->buf->file_last - cl->buf->file_pos);

        if (ngx_buf_size(cl->buf) == 0 && !ngx_buf_special(cl->buf)) {
            ngx_log_error(NGX_LOG_ALERT, c->log, 0,
                          "zero size buf in writer "
                          "t:%d r:%d f:%d %p %p-%p %p %O-%O",
                          cl->buf->temporary,
                          cl->buf->recycled,
                          cl->buf->in_file,
                          cl->buf->start,
                          cl->buf->pos,
                          cl->buf->last,
                          cl->buf->file,
                          cl->buf->file_pos,
                          cl->buf->file_last);

            ngx_debug_point();
            return NGX_ERROR;
        }

        if (ngx_buf_size(cl->buf) < 0) {
            ngx_log_error(NGX_LOG_ALERT, c->log, 0,
                          "negative size buf in writer "
                          "t:%d r:%d f:%d %p %p-%p %p %O-%O",
                          cl->buf->temporary,
                          cl->buf->recycled,
                          cl->buf->in_file,
                          cl->buf->start,
                          cl->buf->pos,
                          cl->buf->last,
                          cl->buf->file,
                          cl->buf->file_pos,
                          cl->buf->file_last);

            ngx_debug_point();
            return NGX_ERROR;
        }

        size += ngx_buf_size(cl->buf);

        if (cl->buf->flush || cl->buf->recycled) {
            flush = 1;
        }

        if (cl->buf->sync) {
            sync = 1;
        }

        if (cl->buf->last_buf) {
            last = 1;
        }
    }

    *ll = NULL;

    ngx_log_debug3(NGX_LOG_DEBUG_STREAM, c->log, 0,
                   "stream write filter: l:%ui f:%ui s:%O", last, flush, size);

    if (size == 0
        && !(c->buffered & NGX_LOWLEVEL_BUFFERED)
        && !(last && c->need_last_buf)
        && !(flush && c->need_flush_buf))
    {
        if (last || flush || sync) {
            for (cl = *out; cl; /* void */) {
                ln = cl;
                cl = cl->next;
                ngx_free_chain(c->pool, ln);
            }

            *out = NULL;
            c->buffered &= ~NGX_STREAM_WRITE_BUFFERED;

            return NGX_OK;
        }

        ngx_log_error(NGX_LOG_ALERT, c->log, 0,
                      "the stream output chain is empty");

        ngx_debug_point();

        return NGX_ERROR;
    }

    chain = c->send_chain(c, *out, 0);

    ngx_log_debug1(NGX_LOG_DEBUG_STREAM, c->log, 0,
                   "stream write filter %p", chain);

    if (chain == NGX_CHAIN_ERROR) {
        c->error = 1;
        return NGX_ERROR;
    }

    for (cl = *out; cl && cl != chain; /* void */) {
        ln = cl;
        cl = cl->next;
        ngx_free_chain(c->pool, ln);
    }

    *out = chain;

    if (chain) {
        if (c->shared) {
            ngx_log_error(NGX_LOG_ALERT, c->log, 0,
                          "shared connection is busy");
            return NGX_ERROR;
        }

        c->buffered |= NGX_STREAM_WRITE_BUFFERED;
        return NGX_AGAIN;
    }

    c->buffered &= ~NGX_STREAM_WRITE_BUFFERED;

    if (c->buffered & NGX_LOWLEVEL_BUFFERED) {
        return NGX_AGAIN;
    }

    return NGX_OK;
}


static ngx_int_t
ngx_stream_write_filter_init(ngx_conf_t *cf)
{
    ngx_stream_top_filter = ngx_stream_write_filter;

    return NGX_OK;
}