leevis.com nginx http2.0的实现

nginx http2.0的实现

Open vislee opened this issue 7 years ago • 0 comments

在ls回调函数ngx_http_init_connection中。如果支持http2.0协议，则可读事件的回调函数覆写为ngx_http_v2_init。当连接可读时，回调该函数。

ngx_http_v2_init

创建连接结构体h2c，类型为ngx_http_v2_connection_t，一个连接对应一个结构体。
创建h2c->streams_index stream列表。
调用ngx_http_v2_send_settings构件SETTINGS帧，设置SETTINGS_MAX_CONCURRENT_STREAMS、SETTINGS_INITIAL_WINDOW_SIZE、SETTINGS_MAX_FRAME_SIZE。因为该帧是面向链接的而不是流，因此流标识必须为0(ngx_http_v2_write_sid(buf->last, 0))。构件好的帧被保存到h2c->last_out上，h2c类型为ngx_http_v2_connection_s。
调用ngx_http_v2_send_window_update函数构件WINDOW_UPDATE帧，结果被保存到h2c->last_out上。
设置state回调函数为ngx_http_v2_state_preface。
可读事件回调函数为ngx_http_v2_read_handler，可写事件回调函数为ngx_http_v2_write_handler。
调用可读事件的回调函数。

ngx_http_v2_read_handler

调用recv封装的函数读取socket缓存区内容。
调用state回调函数ngx_http_v2_state_preface。判断读取的内容是否为PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n，不是则返回Error Codes帧错误码为PROTOCOL_ERROR。
调用ngx_http_v2_state_head处理帧，或添加回调。
调用ngx_http_v2_send_output_queue发送应答帧。

ngx_http_v2_send_settings

拼装settings帧。每一个帧由ngx_http_v2_out_frame_t来表示，其中first指向帧的缓存链，调用ngx_http_v2_write_len_and_type向缓存链的第一个buf写入Length(24)和Type(8)，细节请参考帧格式。Length+Type共占32bit，低8bit是Type，所以Length+Type的内容就是Length左移8bit与上低8位的Type。buf->last是u_char类型长度1字节8bit，复制Flag后++。接着调用ngx_http_v2_write_sid写31bit的Stream Identifier了和1bit的R。接着该设置Payload了。我们看下settings帧的Payload格式，16bit的Identifier和32bit的Value，调用ngx_http_v2_write_uint16写Identifier，调用ngx_http_v2_write_uint32写Value。最后调用ngx_http_v2_queue_blocked_frame把帧挂到h2c->last_out上。

ngx_http_v2_state_head

解析帧头。调用ngx_http_v2_parse_uint32解析帧的Length(24)和Type(8)。调用ngx_http_v2_parse_length从上述解析出的Length和Type中解析Length。调用ngx_http_v2_parse_sid解析Stream Identifier，32位中最高1bit是R位。调用ngx_http_v2_parse_type从上述解析出的Length和Type解析Type。自此帧头已经解析完了。

ngx_http_v2_frame_states

解析不同的帧的payload。目前有10种类型的帧格式。

ngx_http_v2_state_settings

解析settings帧。先判断settings帧的格式是否正确，然后调用ngx_http_v2_send_settings拼settings帧的ack，最后调用ngx_http_v2_state_settings_params。

ngx_http_v2_run_request

ngx_http_v2_state_headers

解析headers帧。

static u_char *
ngx_http_v2_state_headers(ngx_http_v2_connection_t *h2c, u_char *pos,
    u_char *end)
{
    size_t                   size;
    ngx_uint_t               padded, priority, depend, dependency, excl, weight;
    ngx_uint_t               status;
    ngx_http_v2_node_t      *node;
    ngx_http_v2_stream_t    *stream;
    ngx_http_v2_srv_conf_t  *h2scf;

    // padded标识
    padded = h2c->state.flags & NGX_HTTP_V2_PADDED_FLAG;
    // priority标识
    priority = h2c->state.flags & NGX_HTTP_V2_PRIORITY_FLAG;

    // payload 长度
    size = 0;

    // 设置了padded标识，payload包涵了1个字节的pad
    if (padded) {
        size++;
    }

    // 设置了priority标识，payload包涵了1bit的E，31bit的Stream Dependency和8bit的Weight。共5个字节。
    if (priority) {
        size += sizeof(uint32_t) + 1;
    }

    // 当帧头的length小于等于size说明该帧payload格式错误
    if (h2c->state.length < size) {
        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                      "client sent HEADERS frame with incorrect length %uz",
                      h2c->state.length);

        return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_SIZE_ERROR);
    }

    if (h2c->state.length == size) {
        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                      "client sent HEADERS frame with empty header block");

        return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_SIZE_ERROR);
    }

    if (h2c->goaway) {
        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
                       "skipping http2 HEADERS frame");
        return ngx_http_v2_state_skip(h2c, pos, end);
    }

    if ((size_t) (end - pos) < size) {
        return ngx_http_v2_state_save(h2c, pos, end,
                                      ngx_http_v2_state_headers);
    }

    h2c->state.length -= size;

    // 解析pad，填充长度
    if (padded) {
        h2c->state.padding = *pos++;

        if (h2c->state.padding > h2c->state.length) {
            ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                          "client sent padded HEADERS frame "
                          "with incorrect length: %uz, padding: %uz",
                          h2c->state.length, h2c->state.padding);

            return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_SIZE_ERROR);
        }

        h2c->state.length -= h2c->state.padding;
    }

    depend = 0;
    excl = 0;
    weight = 16;

    if (priority) {
        dependency = ngx_http_v2_parse_uint32(pos);
        // depend 该流所依赖的流
        depend = dependency & 0x7fffffff;
        // E标识
        excl = dependency >> 31;
        // 该流的优先级权重
        weight = pos[4] + 1;

        pos += sizeof(uint32_t) + 1;
    }

    ngx_log_debug4(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
                   "http2 HEADERS frame sid:%ui on %ui excl:%ui weight:%ui",
                   h2c->state.sid, depend, excl, weight);

    // 客户端发起的流标识是基数的流
    if (h2c->state.sid % 2 == 0 || h2c->state.sid <= h2c->last_sid) {
        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                      "client sent HEADERS frame with incorrect identifier "
                      "%ui, the last was %ui", h2c->state.sid, h2c->last_sid);

        return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_PROTOCOL_ERROR);
    }

    h2c->last_sid = h2c->state.sid;

    h2c->state.pool = ngx_create_pool(1024, h2c->connection->log);
    if (h2c->state.pool == NULL) {
        return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_INTERNAL_ERROR);
    }

    if (depend == h2c->state.sid) {
        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                      "client sent HEADERS frame for stream %ui "
                      "with incorrect dependency", h2c->state.sid);

        status = NGX_HTTP_V2_PROTOCOL_ERROR;
        goto rst_stream;
    }

    h2scf = ngx_http_get_module_srv_conf(h2c->http_connection->conf_ctx,
                                         ngx_http_v2_module);

    h2c->state.header_limit = h2scf->max_header_size;

    if (h2c->processing >= h2scf->concurrent_streams) {
        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                      "concurrent streams exceeded %ui", h2c->processing);

        status = NGX_HTTP_V2_REFUSED_STREAM;
        goto rst_stream;
    }

    if (!h2c->settings_ack
        && !(h2c->state.flags & NGX_HTTP_V2_END_STREAM_FLAG)
        && h2scf->preread_size < NGX_HTTP_V2_DEFAULT_WINDOW)
    {
        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                      "client sent stream with data "
                      "before settings were acknowledged");

        status = NGX_HTTP_V2_REFUSED_STREAM;
        goto rst_stream;
    }

    node = ngx_http_v2_get_node_by_id(h2c, h2c->state.sid, 1);

    if (node == NULL) {
        return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_INTERNAL_ERROR);
    }

    if (node->parent) {
        ngx_queue_remove(&node->reuse);
        h2c->closed_nodes--;
    }

    stream = ngx_http_v2_create_stream(h2c);
    if (stream == NULL) {
        return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_INTERNAL_ERROR);
    }

    h2c->state.stream = stream;

    stream->pool = h2c->state.pool;
    h2c->state.keep_pool = 1;

    stream->request->request_length = h2c->state.length;

    stream->in_closed = h2c->state.flags & NGX_HTTP_V2_END_STREAM_FLAG;
    stream->node = node;

    node->stream = stream;

    if (priority || node->parent == NULL) {
        node->weight = weight;
        ngx_http_v2_set_dependency(h2c, node, depend, excl);
    }

    if (h2c->connection->requests >= h2scf->max_requests) {
        h2c->goaway = 1;

        if (ngx_http_v2_send_goaway(h2c, NGX_HTTP_V2_NO_ERROR) == NGX_ERROR) {
            return ngx_http_v2_connection_error(h2c,
                                                NGX_HTTP_V2_INTERNAL_ERROR);
        }
    }

    return ngx_http_v2_state_header_block(h2c, pos, end);

rst_stream:

    if (ngx_http_v2_send_rst_stream(h2c, h2c->state.sid, status) != NGX_OK) {
        return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_INTERNAL_ERROR);
    }

    return ngx_http_v2_state_header_block(h2c, pos, end);
}

http2 头部编码： https://imququ.com/post/header-compression-in-http2.html

代码分析

组装帧头

// 一个帧结构体
struct ngx_http_v2_out_frame_s {
    ngx_http_v2_out_frame_t         *next;
    ngx_chain_t                     *first;
    ngx_chain_t                     *last;
    ngx_int_t                      (*handler)(ngx_http_v2_connection_t *h2c,
                                        ngx_http_v2_out_frame_t *frame);

    ngx_http_v2_stream_t            *stream;
    size_t                           length;

    unsigned                         blocked:1;
    unsigned                         fin:1;
};

static ngx_http_v2_out_frame_t *
ngx_http_v2_get_frame(ngx_http_v2_connection_t *h2c, size_t length,
    ngx_uint_t type, u_char flags, ngx_uint_t sid)
{
    ngx_buf_t                *buf;
    ngx_pool_t               *pool;
    ngx_http_v2_out_frame_t  *frame;

    frame = h2c->free_frames;

    if (frame) {
        h2c->free_frames = frame->next;

        buf = frame->first->buf;
        buf->pos = buf->start;

        frame->blocked = 0;

    } else {
        pool = h2c->pool ? h2c->pool : h2c->connection->pool;

        frame = ngx_pcalloc(pool, sizeof(ngx_http_v2_out_frame_t));
        if (frame == NULL) {
            return NULL;
        }

        frame->first = ngx_alloc_chain_link(pool);
        if (frame->first == NULL) {
            return NULL;
        }

        buf = ngx_create_temp_buf(pool, NGX_HTTP_V2_FRAME_BUFFER_SIZE);
        if (buf == NULL) {
            return NULL;
        }

        buf->last_buf = 1;

        frame->first->buf = buf;
        frame->last = frame->first;

        frame->handler = ngx_http_v2_frame_handler;
    }

#if (NGX_DEBUG)
    if (length > NGX_HTTP_V2_FRAME_BUFFER_SIZE - NGX_HTTP_V2_FRAME_HEADER_SIZE)
    {
        ngx_log_error(NGX_LOG_ALERT, h2c->connection->log, 0,
                      "requested control frame is too large: %uz", length);
        return NULL;
    }

    frame->length = length;
#endif

    // length(24) + type(8) 共4B 以网络字节序写入buf这块内存
    buf->last = ngx_http_v2_write_len_and_type(buf->pos, length, type);

    // flags(8)
    *buf->last++ = flags;

    // R(1) + stream ID(31) = 32bit
    buf->last = ngx_http_v2_write_sid(buf->last, sid);

    return frame;
}

组装settings帧

static ngx_int_t
ngx_http_v2_send_settings(ngx_http_v2_connection_t *h2c)
{
    size_t                    len;
    ngx_buf_t                *buf;
    ngx_chain_t              *cl;
    ngx_http_v2_srv_conf_t   *h2scf;
    ngx_http_v2_out_frame_t  *frame;

    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
                   "http2 send SETTINGS frame");

    frame = ngx_palloc(h2c->pool, sizeof(ngx_http_v2_out_frame_t));
    if (frame == NULL) {
        return NGX_ERROR;
    }

    cl = ngx_alloc_chain_link(h2c->pool);
    if (cl == NULL) {
        return NGX_ERROR;
    }

    // 一个settings帧payload的大小是48bit = 6B。
    //  Identifier (16) + Value (32)  = 48bit
    // 设置3个
    len = NGX_HTTP_V2_SETTINGS_PARAM_SIZE * 3;

    // NGX_HTTP_V2_FRAME_HEADER_SIZE frame header 9B = 72bit
    // Length(24)  + Type(8) +  Flags(8）+ R(1) + Stream Identifier(31)   = 72bit
    // 9B + 6B * 3 = 27B
    buf = ngx_create_temp_buf(h2c->pool, NGX_HTTP_V2_FRAME_HEADER_SIZE + len);
    if (buf == NULL) {
        return NGX_ERROR;
    }

    buf->last_buf = 1;

    cl->buf = buf;
    cl->next = NULL;

    frame->first = cl;
    frame->last = cl;
    frame->handler = ngx_http_v2_settings_frame_handler;
    frame->stream = NULL;
#if (NGX_DEBUG)
    frame->length = len;
#endif
    frame->blocked = 0;

    buf->last = ngx_http_v2_write_len_and_type(buf->last, len,
                                               NGX_HTTP_V2_SETTINGS_FRAME);

    *buf->last++ = NGX_HTTP_V2_NO_FLAG;

    buf->last = ngx_http_v2_write_sid(buf->last, 0);

    h2scf = ngx_http_get_module_srv_conf(h2c->http_connection->conf_ctx,
                                         ngx_http_v2_module);

    buf->last = ngx_http_v2_write_uint16(buf->last,
                                         NGX_HTTP_V2_MAX_STREAMS_SETTING);
    buf->last = ngx_http_v2_write_uint32(buf->last,
                                         h2scf->concurrent_streams);

    buf->last = ngx_http_v2_write_uint16(buf->last,
                                         NGX_HTTP_V2_INIT_WINDOW_SIZE_SETTING);
    buf->last = ngx_http_v2_write_uint32(buf->last, h2scf->preread_size);

    buf->last = ngx_http_v2_write_uint16(buf->last,
                                         NGX_HTTP_V2_MAX_FRAME_SIZE_SETTING);
    buf->last = ngx_http_v2_write_uint32(buf->last,
                                         NGX_HTTP_V2_MAX_FRAME_SIZE);

    // 把该frame挂载到h2c->last_out 这个链表的后面。
    ngx_http_v2_queue_blocked_frame(h2c, frame);

    return NGX_OK;
}

可读回调函数：


static void
ngx_http_v2_read_handler(ngx_event_t *rev)
{
    u_char                    *p, *end;
    size_t                     available;
    ssize_t                    n;
    ngx_connection_t          *c;
    ngx_http_v2_main_conf_t   *h2mcf;
    ngx_http_v2_connection_t  *h2c;

    c = rev->data;
    h2c = c->data;

    if (rev->timedout) {
        ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT, "client timed out");
        ngx_http_v2_finalize_connection(h2c, NGX_HTTP_V2_PROTOCOL_ERROR);
        return;
    }

    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, c->log, 0, "http2 read handler");

    h2c->blocked = 1;

    if (c->close) {
        c->close = 0;

        if (!h2c->goaway) {
            h2c->goaway = 1;

            if (ngx_http_v2_send_goaway(h2c, NGX_HTTP_V2_NO_ERROR)
                == NGX_ERROR)
            {
                ngx_http_v2_finalize_connection(h2c, 0);
                return;
            }

            if (ngx_http_v2_send_output_queue(h2c) == NGX_ERROR) {
                ngx_http_v2_finalize_connection(h2c, 0);
                return;
            }
        }

        h2c->blocked = 0;

        return;
    }

    h2mcf = ngx_http_get_module_main_conf(h2c->http_connection->conf_ctx,
                                          ngx_http_v2_module);

    available = h2mcf->recv_buffer_size - 2 * NGX_HTTP_V2_STATE_BUFFER_SIZE;

    do {
        p = h2mcf->recv_buffer;

        ngx_memcpy(p, h2c->state.buffer, NGX_HTTP_V2_STATE_BUFFER_SIZE);
        end = p + h2c->state.buffer_used;

        n = c->recv(c, end, available);

        if (n == NGX_AGAIN) {
            break;
        }

        if (n == 0
            && (h2c->state.incomplete || h2c->processing || h2c->pushing))
        {
            ngx_log_error(NGX_LOG_INFO, c->log, 0,
                          "client prematurely closed connection");
        }

        if (n == 0 || n == NGX_ERROR) {
            c->error = 1;
            ngx_http_v2_finalize_connection(h2c, 0);
            return;
        }

        end += n;

        // 把读取到未解析的内容保存在state.buffer字符数组中
        h2c->state.buffer_used = 0;
        h2c->state.incomplete = 0;

        do {
            // 如果没有四层代理协议，则handler是ngx_http_v2_state_preface函数
            // ngx_http_v2_state_preface 和 ngx_http_v2_state_preface_end 是处理
            // h2 connection preface 见：http://httpwg.org/specs/rfc7540.html#ConnectionHeader 
            // 如果剩余的内容不是一个完整的帧，没有处理完毕，剩余的内容会调用
            // ngx_http_v2_state_save函数，保存在state这个结构体中。
            // 接着调用ngx_http_v2_state_head 处理frame head
            p = h2c->state.handler(h2c, p, end);

            if (p == NULL) {
                return;
            }

        } while (p != end);

    } while (rev->ready);

    if (ngx_handle_read_event(rev, 0) != NGX_OK) {
        ngx_http_v2_finalize_connection(h2c, NGX_HTTP_V2_INTERNAL_ERROR);
        return;
    }

    if (h2c->last_out && ngx_http_v2_send_output_queue(h2c) == NGX_ERROR) {
        ngx_http_v2_finalize_connection(h2c, 0);
        return;
    }

    h2c->blocked = 0;

    if (h2c->processing || h2c->pushing) {
        if (rev->timer_set) {
            ngx_del_timer(rev);
        }

        return;
    }

    ngx_http_v2_handle_connection(h2c);
}


// 处理帧头
static u_char *
ngx_http_v2_state_head(ngx_http_v2_connection_t *h2c, u_char *pos, u_char *end)
{
    uint32_t    head;
    ngx_uint_t  type;

    // 如果长度不够保存下来
    if (end - pos < NGX_HTTP_V2_FRAME_HEADER_SIZE) {
        return ngx_http_v2_state_save(h2c, pos, end, ngx_http_v2_state_head);
    }

    // 32bit 包含了length(24) 和type(8)
    head = ngx_http_v2_parse_uint32(pos);

    h2c->state.length = ngx_http_v2_parse_length(head);
    h2c->state.flags = pos[4];    // 第4字节 [32bit-40bit)

    h2c->state.sid = ngx_http_v2_parse_sid(&pos[5]);

    pos += NGX_HTTP_V2_FRAME_HEADER_SIZE;
    // 帧头处理结束

    // 32bit 高8位
    // type定义：http://httpwg.org/specs/rfc7540.html#iana-frames
    type = ngx_http_v2_parse_type(head);

    ngx_log_debug4(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
                   "http2 frame type:%ui f:%Xd l:%uz sid:%ui",
                   type, h2c->state.flags, h2c->state.length, h2c->state.sid);

    if (type >= NGX_HTTP_V2_FRAME_STATES) {
        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                      "client sent frame with unknown type %ui", type);
        return ngx_http_v2_state_skip(h2c, pos, end);
    }

    // ngx_http_v2_frame_states 是定义了帧处理回调函数的数组
    return ngx_http_v2_frame_states[type](h2c, pos, end);
}

ngx_http_v2_state_headers HEADERS FRAME 处理函数

static u_char *
ngx_http_v2_state_headers(ngx_http_v2_connection_t *h2c, u_char *pos,
    u_char *end)
{
    size_t                   size;
    ngx_uint_t               padded, priority, depend, dependency, excl, weight;
    ngx_uint_t               status;
    ngx_http_v2_node_t      *node;
    ngx_http_v2_stream_t    *stream;
    ngx_http_v2_srv_conf_t  *h2scf;

    // 是否有payload填充
    padded = h2c->state.flags & NGX_HTTP_V2_PADDED_FLAG;
    // 是否有依赖的stream
    priority = h2c->state.flags & NGX_HTTP_V2_PRIORITY_FLAG;

    size = 0;
    // 填充长度占1字节
    if (padded) {
        size++;
    }
    // 依赖stream 占5字节
    if (priority) {
        size += sizeof(uint32_t) + 1;
    }

    if (h2c->state.length < size) {
        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                      "client sent HEADERS frame with incorrect length %uz",
                      h2c->state.length);

        return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_SIZE_ERROR);
    }

    if (h2c->state.length == size) {
        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                      "client sent HEADERS frame with empty header block");

        return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_SIZE_ERROR);
    }

    if (h2c->goaway) {
        ngx_log_debug0(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
                       "skipping http2 HEADERS frame");
        return ngx_http_v2_state_skip(h2c, pos, end);
    }

    if ((size_t) (end - pos) < size) {
        return ngx_http_v2_state_save(h2c, pos, end,
                                      ngx_http_v2_state_headers);
    }

    h2c->state.length -= size;

    if (padded) {
        // 解析填充字段长度字节为单位

        // 填充字节大小
        h2c->state.padding = *pos++;

        if (h2c->state.padding > h2c->state.length) {
            ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                          "client sent padded HEADERS frame "
                          "with incorrect length: %uz, padding: %uz",
                          h2c->state.length, h2c->state.padding);

            return ngx_http_v2_connection_error(h2c,
                                                NGX_HTTP_V2_PROTOCOL_ERROR);
        }

        // 剩余的真实的paylo大小
        h2c->state.length -= h2c->state.padding;
    }

    depend = 0;
    excl = 0;
    weight = NGX_HTTP_V2_DEFAULT_WEIGHT;

    if (priority) {
        dependency = ngx_http_v2_parse_uint32(pos);

        depend = dependency & 0x7fffffff;
        excl = dependency >> 31;
        weight = pos[4] + 1;

        pos += sizeof(uint32_t) + 1;
    }

    ngx_log_debug4(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
                   "http2 HEADERS frame sid:%ui "
                   "depends on %ui excl:%ui weight:%ui",
                   h2c->state.sid, depend, excl, weight);

    // 客户端发起的请求的stream ID 是奇数
    if (h2c->state.sid % 2 == 0 || h2c->state.sid <= h2c->last_sid) {
        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                      "client sent HEADERS frame with incorrect identifier "
                      "%ui, the last was %ui", h2c->state.sid, h2c->last_sid);

        return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_PROTOCOL_ERROR);
    }

    h2c->last_sid = h2c->state.sid;

    h2c->state.pool = ngx_create_pool(1024, h2c->connection->log);
    if (h2c->state.pool == NULL) {
        return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_INTERNAL_ERROR);
    }

    if (depend == h2c->state.sid) {
        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                      "client sent HEADERS frame for stream %ui "
                      "with incorrect dependency", h2c->state.sid);

        status = NGX_HTTP_V2_PROTOCOL_ERROR;
        goto rst_stream;
    }

    h2scf = ngx_http_get_module_srv_conf(h2c->http_connection->conf_ctx,
                                         ngx_http_v2_module);

    h2c->state.header_limit = h2scf->max_header_size;

    // processing 当前处理的流的数目
    if (h2c->processing >= h2scf->concurrent_streams) {
        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                      "concurrent streams exceeded %ui", h2c->processing);

        status = NGX_HTTP_V2_REFUSED_STREAM;
        goto rst_stream;
    }

    if (!h2c->settings_ack
        && !(h2c->state.flags & NGX_HTTP_V2_END_STREAM_FLAG)
        && h2scf->preread_size < NGX_HTTP_V2_DEFAULT_WINDOW)
    {
        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                      "client sent stream with data "
                      "before settings were acknowledged");

        status = NGX_HTTP_V2_REFUSED_STREAM;
        goto rst_stream;
    }

    // 获取一个节点，
    node = ngx_http_v2_get_node_by_id(h2c, h2c->state.sid, 1);

    if (node == NULL) {
        return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_INTERNAL_ERROR);
    }

    if (node->parent) {
        ngx_queue_remove(&node->reuse);
        h2c->closed_nodes--;
    }

    // 创建一个请求流结构体，同时对应一个请求
    stream = ngx_http_v2_create_stream(h2c, 0);
    if (stream == NULL) {
        return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_INTERNAL_ERROR);
    }

    h2c->state.stream = stream;

    stream->pool = h2c->state.pool;
    h2c->state.keep_pool = 1;

    stream->request->request_length = h2c->state.length;

    stream->in_closed = h2c->state.flags & NGX_HTTP_V2_END_STREAM_FLAG;
    stream->node = node;

    node->stream = stream;

    if (priority || node->parent == NULL) {
        node->weight = weight;
        ngx_http_v2_set_dependency(h2c, node, depend, excl);
    }

    if (h2c->connection->requests >= h2scf->max_requests) {
        h2c->goaway = 1;

        if (ngx_http_v2_send_goaway(h2c, NGX_HTTP_V2_NO_ERROR) == NGX_ERROR) {
            return ngx_http_v2_connection_error(h2c,
                                                NGX_HTTP_V2_INTERNAL_ERROR);
        }
    }

    return ngx_http_v2_state_header_block(h2c, pos, end);

rst_stream:

    if (ngx_http_v2_send_rst_stream(h2c, h2c->state.sid, status) != NGX_OK) {
        return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_INTERNAL_ERROR);
    }

    return ngx_http_v2_state_header_block(h2c, pos, end);
}


// 解析header的[HPACK](http://httpwg.org/specs/rfc7541.html#detailed.format)格式的头

static u_char *
ngx_http_v2_state_header_block(ngx_http_v2_connection_t *h2c, u_char *pos,
    u_char *end)
{
    u_char      ch;
    ngx_int_t   value;
    ngx_uint_t  indexed, size_update, prefix;

    if (end - pos < 1) {
        return ngx_http_v2_state_headers_save(h2c, pos, end,
                                              ngx_http_v2_state_header_block);
    }

    if (!(h2c->state.flags & NGX_HTTP_V2_END_HEADERS_FLAG)
        && h2c->state.length < NGX_HTTP_V2_INT_OCTETS)
    {
        return ngx_http_v2_handle_continuation(h2c, pos, end,
                                               ngx_http_v2_state_header_block);
    }

    size_update = 0;
    indexed = 0;

    ch = *pos;

    if (ch >= (1 << 7)) {
        // http://httpwg.org/specs/rfc7541.html#indexed.header.representation
        /* indexed header field */
        indexed = 1;
        // (1 << 7) -1  6bit全是1.
        prefix = ngx_http_v2_prefix(7);

    } else if (ch >= (1 << 6)) {
        /* literal header field with incremental indexing */
        h2c->state.index = 1;
        prefix = ngx_http_v2_prefix(6);

    } else if (ch >= (1 << 5)) {
        /* dynamic table size update */
        size_update = 1;
        prefix = ngx_http_v2_prefix(5);

    } else if (ch >= (1 << 4)) {
        /* literal header field never indexed */
        prefix = ngx_http_v2_prefix(4);

    } else {
        /* literal header field without indexing */
        prefix = ngx_http_v2_prefix(4);
    }

    // 解析HPACK 的整数编码
    // value 是表中的下标
    value = ngx_http_v2_parse_int(h2c, &pos, end, prefix);

    if (value < 0) {
        if (value == NGX_AGAIN) {
            return ngx_http_v2_state_headers_save(h2c, pos, end,
                                               ngx_http_v2_state_header_block);
        }

        if (value == NGX_DECLINED) {
            ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                          "client sent header block with too long %s value",
                          size_update ? "size update" : "header index");

            return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_COMP_ERROR);
        }

        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                      "client sent header block with incorrect length");

        return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_SIZE_ERROR);
    }

    if (indexed) {
        // 静态table 索引
        if (ngx_http_v2_get_indexed_header(h2c, value, 0) != NGX_OK) {
            return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_COMP_ERROR);
        }

        return ngx_http_v2_state_process_header(h2c, pos, end);
    }

    if (size_update) {
        if (ngx_http_v2_table_size(h2c, value) != NGX_OK) {
            return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_COMP_ERROR);
        }

        return ngx_http_v2_state_header_complete(h2c, pos, end);
    }

    if (value == 0) {
        h2c->state.parse_name = 1;

    } else if (ngx_http_v2_get_indexed_header(h2c, value, 1) != NGX_OK) {
        return ngx_http_v2_connection_error(h2c, NGX_HTTP_V2_COMP_ERROR);
    }

    h2c->state.parse_value = 1;

    return ngx_http_v2_state_field_len(h2c, pos, end);
}

创建一个流，一个流对应一个请求。一个连接包含多个流，一个流包含多个帧。这个函数是适配nginx http 框架的核心


static ngx_http_v2_stream_t *
ngx_http_v2_create_stream(ngx_http_v2_connection_t *h2c, ngx_uint_t push)
{
    ngx_log_t                 *log;
    ngx_event_t               *rev, *wev;
    ngx_connection_t          *fc;
    ngx_http_log_ctx_t        *ctx;
    ngx_http_request_t        *r;
    ngx_http_v2_stream_t      *stream;
    ngx_http_v2_srv_conf_t    *h2scf;
    ngx_http_core_srv_conf_t  *cscf;

    fc = h2c->free_fake_connections;

    if (fc) {
        h2c->free_fake_connections = fc->data;

        rev = fc->read;
        wev = fc->write;
        log = fc->log;
        ctx = log->data;

    } else {
        // 创建一个 虚拟连接
        fc = ngx_palloc(h2c->pool, sizeof(ngx_connection_t));
        if (fc == NULL) {
            return NULL;
        }

        // 虚拟连接可读回调
        rev = ngx_palloc(h2c->pool, sizeof(ngx_event_t));
        if (rev == NULL) {
            return NULL;
        }

        wev = ngx_palloc(h2c->pool, sizeof(ngx_event_t));
        if (wev == NULL) {
            return NULL;
        }

        log = ngx_palloc(h2c->pool, sizeof(ngx_log_t));
        if (log == NULL) {
            return NULL;
        }

        ctx = ngx_palloc(h2c->pool, sizeof(ngx_http_log_ctx_t));
        if (ctx == NULL) {
            return NULL;
        }

        ctx->connection = fc;
        ctx->request = NULL;
        ctx->current_request = NULL;
    }

    ngx_memcpy(log, h2c->connection->log, sizeof(ngx_log_t));

    log->data = ctx;

    if (push) {
        log->action = "processing pushed request headers";

    } else {
        log->action = "reading client request headers";
    }

    ngx_memzero(rev, sizeof(ngx_event_t));

    rev->data = fc;
    rev->ready = 1;
    rev->handler = ngx_http_v2_close_stream_handler;
    rev->log = log;

    ngx_memcpy(wev, rev, sizeof(ngx_event_t));

    wev->write = 1;

    ngx_memcpy(fc, h2c->connection, sizeof(ngx_connection_t));

    fc->data = h2c->http_connection;
    fc->read = rev;
    fc->write = wev;
    fc->sent = 0;
    fc->log = log;
    fc->buffered = 0;
    fc->sndlowat = 1;
    fc->tcp_nodelay = NGX_TCP_NODELAY_DISABLED;

    // 和http1 就一样了，创建一个请求结构体
    r = ngx_http_create_request(fc);
    if (r == NULL) {
        return NULL;
    }

    // 强制设置http2.0协议
    ngx_str_set(&r->http_protocol, "HTTP/2.0");

    r->http_version = NGX_HTTP_VERSION_20;
    r->valid_location = 1;

    fc->data = r;
    h2c->connection->requests++;

    cscf = ngx_http_get_module_srv_conf(r, ngx_http_core_module);

    // 创建一个保存请求的buffer
    r->header_in = ngx_create_temp_buf(r->pool,
                                       cscf->client_header_buffer_size);
    if (r->header_in == NULL) {
        ngx_http_free_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
        return NULL;
    }

    // 创建请求头
    if (ngx_list_init(&r->headers_in.headers, r->pool, 20,
                      sizeof(ngx_table_elt_t))
        != NGX_OK)
    {
        ngx_http_free_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
        return NULL;
    }

    // 对于请求而言没有长连接
    r->headers_in.connection_type = NGX_HTTP_CONNECTION_CLOSE;

    stream = ngx_pcalloc(r->pool, sizeof(ngx_http_v2_stream_t));
    if (stream == NULL) {
        ngx_http_free_request(r, NGX_HTTP_INTERNAL_SERVER_ERROR);
        return NULL;
    }

    r->stream = stream;

    stream->request = r;
    stream->connection = h2c;

    h2scf = ngx_http_get_module_srv_conf(r, ngx_http_v2_module);

    stream->send_window = h2c->init_window;
    stream->recv_window = h2scf->preread_size;

    if (push) {
        h2c->pushing++;

    } else {
        h2c->processing++;
    }

    return stream;
}

文件 ngx_http_v2_table.c

// 解析HPACK协议的header头
ngx_int_t
ngx_http_v2_get_indexed_header(ngx_http_v2_connection_t *h2c, ngx_uint_t index,
    ngx_uint_t name_only)
{
    u_char                *p;
    size_t                 rest;
    ngx_http_v2_header_t  *entry;

    if (index == 0) {
        ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                      "client sent invalid hpack table index 0");
        return NGX_ERROR;
    }

    ngx_log_debug2(NGX_LOG_DEBUG_HTTP, h2c->connection->log, 0,
                   "http2 get indexed %s: %ui",
                   name_only ? "name" : "header", index);

    index--;

    // 是否是静态表的头
    if (index < NGX_HTTP_V2_STATIC_TABLE_ENTRIES) {
        h2c->state.header = ngx_http_v2_static_table[index];
        return NGX_OK;
    }

    index -= NGX_HTTP_V2_STATIC_TABLE_ENTRIES;

    if (index < h2c->hpack.added - h2c->hpack.deleted) {
        index = (h2c->hpack.added - index - 1) % h2c->hpack.allocated;
        entry = h2c->hpack.entries[index];

        p = ngx_pnalloc(h2c->state.pool, entry->name.len + 1);
        if (p == NULL) {
            return NGX_ERROR;
        }

        h2c->state.header.name.len = entry->name.len;
        h2c->state.header.name.data = p;

        rest = h2c->hpack.storage + NGX_HTTP_V2_TABLE_SIZE - entry->name.data;

        if (entry->name.len > rest) {
            p = ngx_cpymem(p, entry->name.data, rest);
            p = ngx_cpymem(p, h2c->hpack.storage, entry->name.len - rest);

        } else {
            p = ngx_cpymem(p, entry->name.data, entry->name.len);
        }

        *p = '\0';

        if (name_only) {
            return NGX_OK;
        }

        p = ngx_pnalloc(h2c->state.pool, entry->value.len + 1);
        if (p == NULL) {
            return NGX_ERROR;
        }

        h2c->state.header.value.len = entry->value.len;
        h2c->state.header.value.data = p;

        rest = h2c->hpack.storage + NGX_HTTP_V2_TABLE_SIZE - entry->value.data;

        if (entry->value.len > rest) {
            p = ngx_cpymem(p, entry->value.data, rest);
            p = ngx_cpymem(p, h2c->hpack.storage, entry->value.len - rest);

        } else {
            p = ngx_cpymem(p, entry->value.data, entry->value.len);
        }

        *p = '\0';

        return NGX_OK;
    }

    ngx_log_error(NGX_LOG_INFO, h2c->connection->log, 0,
                  "client sent out of bound hpack table index: %ui", index);

    return NGX_ERROR;
}

修改nginx返回的server：

在ngx_http_v2_filter_module.c 文件中有以下定义： static const u_char nginx[5] = "\x84\xaa\x63\x55\xe7"; 修改一下。

package main

import (
    "fmt"
    "golang.org/x/net/http2/hpack"
)

func main() {
    fmt.Println("nginx", "→", Encode("nginx"))
    fmt.Println("apache", "→", Encode("apache"))
    fmt.Println("-----")
    fmt.Println("\\x84\\xaa\\x63\\x55\\xe7", "→", Decode("\x84\xaa\x63\x55\xe7"))
    fmt.Println("\\x84\\x1d\\x63\\x24\\xe5", "→", Decode("\x84\x1d\x63\x24\xe5"))
}

func Encode(s string) string {
    var result string

    hd := hpack.AppendHuffmanString(nil, s)
    hl := hpack.HuffmanEncodeLength(s) | 0x80

    result += RenderByte(byte(hl))

    for _, b := range hd {
        result += RenderByte(b)
    }

    return result
}

func Decode(s string) string {
    data := []byte(s)
    result, _ := hpack.HuffmanDecodeToString(data[1:])
    return result
}

func RenderByte(b byte) string {
    return fmt.Sprintf("\\x%x", b)
}

Mar 02 '17 11:03 vislee

leevis.com leevis.com copied to clipboard

nginx http2.0的实现

ngx_http_v2_init

ngx_http_v2_read_handler

ngx_http_v2_send_settings

ngx_http_v2_state_head

ngx_http_v2_frame_states

ngx_http_v2_state_settings

ngx_http_v2_run_request

ngx_http_v2_state_headers

代码分析

修改nginx返回的server：

leevis.com
leevis.com copied to clipboard