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view src/http/modules/ngx_http_chunked_filter_module.c @ 7281:bd6563e81cea

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Limit req: improved handling of negative times. Negative times can appear since workers only update time on an event loop iteration start. If a worker was blocked for a long time during an event loop iteration, it is possible that another worker already updated the time stored in the node. As such, time since last update of the node (ms) will be negative. Previous code used ngx_abs(ms) in the calculations. That is, negative times were effectively treated as positive ones. As a result, it was not possible to maintain high request rates, where the same node can be updated multiple times from during an event loop iteration. In particular, this affected setups with many SSL handshakes, see http://mailman.nginx.org/pipermail/nginx/2018-May/056291.html. Fix is to only update the last update time stored in the node if the new time is larger than previously stored one. If a future time is stored in the node, we preserve this time as is. To prevent breaking things on platforms without monotonic time available if system time is updated backwards, a safety limit of 60 seconds is used. If the time stored in the node is more than 60 seconds in the future, we assume that the time was changed backwards and update lr->last to the current time.
author Maxim Dounin <mdounin@mdounin.ru>
date Wed, 30 May 2018 15:40:34 +0300
parents 1b068a4e82d8
children 46e3542d51b3
line wrap: on
line source


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


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


typedef struct {
    ngx_chain_t         *free;
    ngx_chain_t         *busy;
} ngx_http_chunked_filter_ctx_t;


static ngx_int_t ngx_http_chunked_filter_init(ngx_conf_t *cf);
static ngx_chain_t *ngx_http_chunked_create_trailers(ngx_http_request_t *r,
    ngx_http_chunked_filter_ctx_t *ctx);


static ngx_http_module_t  ngx_http_chunked_filter_module_ctx = {
    NULL,                                  /* preconfiguration */
    ngx_http_chunked_filter_init,          /* postconfiguration */

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

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

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


ngx_module_t  ngx_http_chunked_filter_module = {
    NGX_MODULE_V1,
    &ngx_http_chunked_filter_module_ctx,   /* module context */
    NULL,                                  /* module directives */
    NGX_HTTP_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_http_output_header_filter_pt  ngx_http_next_header_filter;
static ngx_http_output_body_filter_pt    ngx_http_next_body_filter;


static ngx_int_t
ngx_http_chunked_header_filter(ngx_http_request_t *r)
{
    ngx_http_core_loc_conf_t       *clcf;
    ngx_http_chunked_filter_ctx_t  *ctx;

    if (r->headers_out.status == NGX_HTTP_NOT_MODIFIED
        || r->headers_out.status == NGX_HTTP_NO_CONTENT
        || r->headers_out.status < NGX_HTTP_OK
        || r != r->main
        || r->method == NGX_HTTP_HEAD)
    {
        return ngx_http_next_header_filter(r);
    }

    if (r->headers_out.content_length_n == -1
        || r->expect_trailers)
    {
        clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);

        if (r->http_version >= NGX_HTTP_VERSION_11
            && clcf->chunked_transfer_encoding)
        {
            if (r->expect_trailers) {
                ngx_http_clear_content_length(r);
            }

            r->chunked = 1;

            ctx = ngx_pcalloc(r->pool, sizeof(ngx_http_chunked_filter_ctx_t));
            if (ctx == NULL) {
                return NGX_ERROR;
            }

            ngx_http_set_ctx(r, ctx, ngx_http_chunked_filter_module);

        } else if (r->headers_out.content_length_n == -1) {
            r->keepalive = 0;
        }
    }

    return ngx_http_next_header_filter(r);
}


static ngx_int_t
ngx_http_chunked_body_filter(ngx_http_request_t *r, ngx_chain_t *in)
{
    u_char                         *chunk;
    off_t                           size;
    ngx_int_t                       rc;
    ngx_buf_t                      *b;
    ngx_chain_t                    *out, *cl, *tl, **ll;
    ngx_http_chunked_filter_ctx_t  *ctx;

    if (in == NULL || !r->chunked || r->header_only) {
        return ngx_http_next_body_filter(r, in);
    }

    ctx = ngx_http_get_module_ctx(r, ngx_http_chunked_filter_module);

    out = NULL;
    ll = &out;

    size = 0;
    cl = in;

    for ( ;; ) {
        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                       "http chunk: %O", ngx_buf_size(cl->buf));

        size += ngx_buf_size(cl->buf);

        if (cl->buf->flush
            || cl->buf->sync
            || ngx_buf_in_memory(cl->buf)
            || cl->buf->in_file)
        {
            tl = ngx_alloc_chain_link(r->pool);
            if (tl == NULL) {
                return NGX_ERROR;
            }

            tl->buf = cl->buf;
            *ll = tl;
            ll = &tl->next;
        }

        if (cl->next == NULL) {
            break;
        }

        cl = cl->next;
    }

    if (size) {
        tl = ngx_chain_get_free_buf(r->pool, &ctx->free);
        if (tl == NULL) {
            return NGX_ERROR;
        }

        b = tl->buf;
        chunk = b->start;

        if (chunk == NULL) {
            /* the "0000000000000000" is 64-bit hexadecimal string */

            chunk = ngx_palloc(r->pool, sizeof("0000000000000000" CRLF) - 1);
            if (chunk == NULL) {
                return NGX_ERROR;
            }

            b->start = chunk;
            b->end = chunk + sizeof("0000000000000000" CRLF) - 1;
        }

        b->tag = (ngx_buf_tag_t) &ngx_http_chunked_filter_module;
        b->memory = 0;
        b->temporary = 1;
        b->pos = chunk;
        b->last = ngx_sprintf(chunk, "%xO" CRLF, size);

        tl->next = out;
        out = tl;
    }

    if (cl->buf->last_buf) {
        tl = ngx_http_chunked_create_trailers(r, ctx);
        if (tl == NULL) {
            return NGX_ERROR;
        }

        cl->buf->last_buf = 0;

        *ll = tl;

        if (size == 0) {
            tl->buf->pos += 2;
        }

    } else if (size > 0) {
        tl = ngx_chain_get_free_buf(r->pool, &ctx->free);
        if (tl == NULL) {
            return NGX_ERROR;
        }

        b = tl->buf;

        b->tag = (ngx_buf_tag_t) &ngx_http_chunked_filter_module;
        b->temporary = 0;
        b->memory = 1;
        b->pos = (u_char *) CRLF;
        b->last = b->pos + 2;

        *ll = tl;

    } else {
        *ll = NULL;
    }

    rc = ngx_http_next_body_filter(r, out);

    ngx_chain_update_chains(r->pool, &ctx->free, &ctx->busy, &out,
                            (ngx_buf_tag_t) &ngx_http_chunked_filter_module);

    return rc;
}


static ngx_chain_t *
ngx_http_chunked_create_trailers(ngx_http_request_t *r,
    ngx_http_chunked_filter_ctx_t *ctx)
{
    size_t            len;
    ngx_buf_t        *b;
    ngx_uint_t        i;
    ngx_chain_t      *cl;
    ngx_list_part_t  *part;
    ngx_table_elt_t  *header;

    len = 0;

    part = &r->headers_out.trailers.part;
    header = part->elts;

    for (i = 0; /* void */; i++) {

        if (i >= part->nelts) {
            if (part->next == NULL) {
                break;
            }

            part = part->next;
            header = part->elts;
            i = 0;
        }

        if (header[i].hash == 0) {
            continue;
        }

        len += header[i].key.len + sizeof(": ") - 1
               + header[i].value.len + sizeof(CRLF) - 1;
    }

    cl = ngx_chain_get_free_buf(r->pool, &ctx->free);
    if (cl == NULL) {
        return NULL;
    }

    b = cl->buf;

    b->tag = (ngx_buf_tag_t) &ngx_http_chunked_filter_module;
    b->temporary = 0;
    b->memory = 1;
    b->last_buf = 1;

    if (len == 0) {
        b->pos = (u_char *) CRLF "0" CRLF CRLF;
        b->last = b->pos + sizeof(CRLF "0" CRLF CRLF) - 1;
        return cl;
    }

    len += sizeof(CRLF "0" CRLF CRLF) - 1;

    b->pos = ngx_palloc(r->pool, len);
    if (b->pos == NULL) {
        return NULL;
    }

    b->last = b->pos;

    *b->last++ = CR; *b->last++ = LF;
    *b->last++ = '0';
    *b->last++ = CR; *b->last++ = LF;

    part = &r->headers_out.trailers.part;
    header = part->elts;

    for (i = 0; /* void */; i++) {

        if (i >= part->nelts) {
            if (part->next == NULL) {
                break;
            }

            part = part->next;
            header = part->elts;
            i = 0;
        }

        if (header[i].hash == 0) {
            continue;
        }

        ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                       "http trailer: \"%V: %V\"",
                       &header[i].key, &header[i].value);

        b->last = ngx_copy(b->last, header[i].key.data, header[i].key.len);
        *b->last++ = ':'; *b->last++ = ' ';

        b->last = ngx_copy(b->last, header[i].value.data, header[i].value.len);
        *b->last++ = CR; *b->last++ = LF;
    }

    *b->last++ = CR; *b->last++ = LF;

    return cl;
}


static ngx_int_t
ngx_http_chunked_filter_init(ngx_conf_t *cf)
{
    ngx_http_next_header_filter = ngx_http_top_header_filter;
    ngx_http_top_header_filter = ngx_http_chunked_header_filter;

    ngx_http_next_body_filter = ngx_http_top_body_filter;
    ngx_http_top_body_filter = ngx_http_chunked_body_filter;

    return NGX_OK;
}