ngx_resolver.c

Nginx是一个高性能的HTTP和反向代理服务器

        }

        ctx->event->handler = ngx_resolver_timeout_handler;
        ctx->event->data = ctx;
        ctx->event->log = r->log;
        ctx->ident = -1;

        ngx_add_timer(ctx->event, ctx->timeout);
    }

    if (ngx_queue_empty(&r->name_resend_queue)) {
        ngx_add_timer(r->event, (ngx_msec_t) (r->resend_timeout * 1000));
    }

    rn->expire = ngx_time() + r->resend_timeout;

    ngx_queue_insert_head(&r->name_resend_queue, &rn->queue);

    rn->cnlen = 0;
    rn->naddrs = 0;
    rn->valid = 0;
    rn->waiting = ctx;

    ctx->state = NGX_AGAIN;

    return NGX_AGAIN;

failed:

    ngx_rbtree_delete(&r->name_rbtree, &rn->node);

    if (rn->query) {
        ngx_resolver_free(r, rn->query);
    }

    ngx_resolver_free(r, rn->name);

    ngx_resolver_free(r, rn);

    return NGX_ERROR;
}


ngx_int_t
ngx_resolve_addr(ngx_resolver_ctx_t *ctx)
{
    ngx_resolver_t       *r;
    ngx_resolver_node_t  *rn;

    r = ctx->resolver;

    ctx->addr = ntohl(ctx->addr);

    /* lock addr mutex */

    rn = ngx_resolver_lookup_addr(r, ctx->addr);

    if (rn) {

        if (rn->valid >= ngx_time()) {

            ngx_log_debug0(NGX_LOG_DEBUG_CORE, r->log, 0, "resolve cached");

            ngx_queue_remove(&rn->queue);

            rn->expire = ngx_time() + r->expire;

            ngx_queue_insert_head(&r->addr_expire_queue, &rn->queue);

            ctx->name.len = rn->nlen;
            ctx->name.data = ngx_resolver_dup(r, rn->name, rn->nlen);
            if (ctx->name.data == NULL) {
                goto failed;
            }

            /* unlock addr mutex */

            ctx->state = NGX_OK;

            ctx->handler(ctx);

            ngx_resolver_free(r, ctx->name.data);

            return NGX_OK;
        }

        if (rn->waiting) {

            ctx->next = rn->waiting;
            rn->waiting = ctx;

            return NGX_AGAIN;
        }

        ngx_queue_remove(&rn->queue);

        ngx_resolver_free(r, rn->query);
        rn->query = NULL;

    } else {
        rn = ngx_resolver_alloc(r, sizeof(ngx_resolver_node_t));
        if (rn == NULL) {
            goto failed;
        }

        rn->node.key = ctx->addr;
        rn->query = NULL;

        ngx_rbtree_insert(&r->addr_rbtree, &rn->node);
    }

    if (ngx_resolver_create_addr_query(rn, ctx) != NGX_OK) {
        goto failed;
    }

    if (ngx_resolver_send_query(r, rn) != NGX_OK) {
        goto failed;
    }

    ctx->event = ngx_resolver_calloc(r, sizeof(ngx_event_t));
    if (ctx->event == NULL) {
        goto failed;
    }

    ctx->event->handler = ngx_resolver_timeout_handler;
    ctx->event->data = ctx;
    ctx->event->log = r->log;
    ctx->ident = -1;

    ngx_add_timer(ctx->event, ctx->timeout);

    if (ngx_queue_empty(&r->addr_resend_queue)) {
        ngx_add_timer(r->event, (ngx_msec_t) (r->resend_timeout * 1000));
    }

    rn->expire = ngx_time() + r->resend_timeout;

    ngx_queue_insert_head(&r->addr_resend_queue, &rn->queue);

    rn->cnlen = 0;
    rn->naddrs = 0;
    rn->name = NULL;
    rn->nlen = 0;
    rn->valid = 0;
    rn->waiting = ctx;

    /* unlock addr mutex */

    ctx->state = NGX_AGAIN;

    return NGX_OK;

failed:

    if (rn) {
        ngx_rbtree_delete(&r->addr_rbtree, &rn->node);

        if (rn->query) {
            ngx_resolver_free(r, rn->query);
        }

        ngx_resolver_free(r, rn);
    }

    /* unlock addr mutex */

    if (ctx->event) {
        ngx_resolver_free(r, ctx->event);
    }

    ngx_resolver_free(r, ctx);

    return NGX_ERROR;
}


void
ngx_resolve_addr_done(ngx_resolver_ctx_t *ctx)
{
    in_addr_t             addr;
    ngx_resolver_t       *r;
    ngx_resolver_ctx_t   *w, **p;
    ngx_resolver_node_t  *rn;

    r = ctx->resolver;

    ngx_log_debug1(NGX_LOG_DEBUG_CORE, r->log, 0,
                   "resolve addr done: %i", ctx->state);

    if (ctx->event && ctx->event->timer_set) {
        ngx_del_timer(ctx->event);
    }

    /* lock addr mutex */

    if (ctx->state == NGX_AGAIN || ctx->state == NGX_RESOLVE_TIMEDOUT) {

        rn = ngx_resolver_lookup_addr(r, ctx->addr);

        if (rn) {
            p = &rn->waiting;
            w = rn->waiting;

            while (w) {
                if (w == ctx) {
                    *p = w->next;

                    goto done;
                }

                p = &w->next;
                w = w->next;
            }
        }

        addr = ntohl(ctx->addr);

        ngx_log_error(NGX_LOG_ALERT, r->log, 0,
                      "could not cancel %ud.%ud.%ud.%ud resolving",
                      (addr >> 24) & 0xff, (addr >> 16) & 0xff,
                      (addr >> 8) & 0xff, addr & 0xff);
    }

done:

    ngx_resolver_expire(r, &r->addr_rbtree, &r->addr_expire_queue);

    /* unlock addr mutex */

    /* lock alloc mutex */

    if (ctx->event) {
        ngx_resolver_free_locked(r, ctx->event);
    }

    ngx_resolver_free_locked(r, ctx);

    /* unlock alloc mutex */
}


static void
ngx_resolver_expire(ngx_resolver_t *r, ngx_rbtree_t *tree, ngx_queue_t *queue)
{
    time_t                now;
    ngx_uint_t            i;
    ngx_queue_t          *q;
    ngx_resolver_node_t  *rn;

    ngx_log_debug0(NGX_LOG_DEBUG_CORE, r->log, 0, "resolver expire");

    now = ngx_time();

    for (i = 0; i < 2; i++) {
        if (ngx_queue_empty(queue)) {
            return;
        }

        q = ngx_queue_last(queue);

        rn = ngx_queue_data(q, ngx_resolver_node_t, queue);

        if (now <= rn->expire) {
            return;
        }

        ngx_log_debug2(NGX_LOG_DEBUG_CORE, r->log, 0,
                       "resolver expire \"%*s\"", (size_t) rn->nlen, rn->name);

        ngx_queue_remove(q);

        ngx_rbtree_delete(tree, &rn->node);

        ngx_resolver_free_node(r, rn);
    }
}


static ngx_int_t
ngx_resolver_send_query(ngx_resolver_t *r, ngx_resolver_node_t *rn)
{
    ssize_t                n;
    ngx_udp_connection_t  *uc;

    uc = r->udp_connection;

    if (uc->connection == NULL) {
        if (ngx_udp_connect(uc) != NGX_OK) {
            return NGX_ERROR;
        }

        uc->connection->data = r;
        uc->connection->read->handler = ngx_resolver_read_response;
        uc->connection->read->resolver = 1;
    }

    n = ngx_send(uc->connection, rn->query, rn->qlen);

    if (n == -1) {
        return NGX_ERROR;
    }

    if ((size_t) n != (size_t) rn->qlen) {
        ngx_log_error(NGX_LOG_CRIT, uc->log, 0, "send() incomplete");
        return NGX_ERROR;
    }

    return NGX_OK;
}


static void
ngx_resolver_resend_handler(ngx_event_t *ev)
{
    time_t           timer, atimer, ntimer;
    ngx_resolver_t  *r;

    r = ev->data;

    ngx_log_debug0(NGX_LOG_DEBUG_CORE, r->log, 0,
                   "resolver resend handler");

    /* lock name mutex */

    ntimer = ngx_resolver_resend(r, &r->name_rbtree, &r->name_resend_queue);

    /* unlock name mutex */

    /* lock addr mutex */

    atimer = ngx_resolver_resend(r, &r->addr_rbtree, &r->addr_resend_queue);

    /* unlock addr mutex */

    if (ntimer == 0) {
        timer = atimer;

    } else if (atimer == 0) {
        timer = ntimer;

    } else {
        timer = (atimer < ntimer) ? atimer : ntimer;
    }

    if (timer) {
        ngx_add_timer(r->event, (ngx_msec_t) (timer * 1000));
    }
}


static time_t
ngx_resolver_resend(ngx_resolver_t *r, ngx_rbtree_t *tree, ngx_queue_t *queue)
{
    time_t                now;
    ngx_queue_t          *q;
    ngx_resolver_node_t  *rn;

    now = ngx_time();

    for ( ;; ) {
        if (ngx_queue_empty(queue)) {
            return 0;
        }

        q = ngx_queue_last(queue);

        rn = ngx_queue_data(q, ngx_resolver_node_t, queue);

        if (now < rn->expire) {
            return rn->expire - now;
        }

        ngx_log_debug3(NGX_LOG_DEBUG_CORE, r->log, 0,
                       "resolver resend \"%*s\" %p",
                       (size_t) rn->nlen, rn->name, rn->waiting);

        ngx_queue_remove(q);

        if (rn->waiting) {

            if (ngx_resolver_send_query(r, rn) == NGX_OK) {

                rn->expire = now + r->resend_timeout;

                ngx_queue_insert_head(queue, &rn->queue);
            }

            continue;
        }

        ngx_rbtree_delete(tree, &rn->node);

        ngx_resolver_free_node(r, rn);
    }
}


static void
ngx_resolver_read_response(ngx_event_t *rev)
{
    ssize_t            n;
    ngx_connection_t  *c;
    u_char             buf[NGX_RESOLVER_UDP_SIZE];

    c = rev->data;

    do {
        n = ngx_udp_recv(c, buf, NGX_RESOLVER_UDP_SIZE);

        if (n < 0) {
            return;
        }

        ngx_resolver_process_response(c->data, buf, n);

    } while (rev->ready);
}


static void
ngx_resolver_process_response(ngx_resolver_t *r, u_char *buf, size_t n)
{
    char                  *err;
    size_t                 len;
    ngx_uint_t             i, ident, flags, code, nqs, nan, qtype, qclass;
    ngx_resolver_qs_t     *qs;
    ngx_resolver_query_t  *query;

    if ((size_t) n < sizeof(ngx_resolver_query_t) + 1) {
        goto short_response;
    }

    query = (ngx_resolver_query_t *) buf;

    ident = (query->ident_hi << 8) + query->ident_lo;
    flags = (query->flags_hi << 8) + query->flags_lo;
    nqs = (query->nqs_hi << 8) + query->nqs_lo;
    nan = (query->nan_hi << 8) + query->nan_lo;

    ngx_log_debug6(NGX_LOG_DEBUG_CORE, r->log, 0,
                   "resolver DNS response %ui fl:%04Xui %ui/%ui/%ui/%ui",
                   ident, flags, nqs, nan,
                   (query->nns_hi << 8) + query->nns_lo,
                   (query->nar_hi << 8) + query->nar_lo);

    if (!(flags & 0x8000)) {
        ngx_log_error(r->log_level, r->log, 0,
                      "invalid DNS response %ui fl:%04Xui", ident, flags);
        return;
    }

    code = flags & 0x7f;

    if (code == NGX_RESOLVE_FORMERR || code > NGX_RESOLVE_REFUSED) {
        ngx_log_error(r->log_level, r->log, 0,
                      "DNS error (%ui: %s), query id:%ui",
                      code, ngx_resolver_strerror(code), ident);
        return;
    }

    if (nqs != 1) {
        err = "invalid number of questions in DNS response";
        goto done;
    }

    i = sizeof(ngx_resolver_query_t);

    while (i < (ngx_uint_t) n) {
        if (buf[i] == '\0') {
            goto found;
        }

        len = buf[i];
        i += 1 + len;
    }

    goto short_response;

found:

    if (i++ == 0) {
        err = "zero-length domain name in DNS response";
        goto done;
    }

    if (i + sizeof(ngx_resolver_qs_t) + nan * (2 + sizeof(ngx_resolver_an_t))
        > (ngx_uint_t) n)
    {
        goto short_response;
    }

    qs = (ngx_resolver_qs_t *) &buf[i];

    qtype = (qs->type_hi << 8) + qs->type_lo;
    qclass = (qs->class_hi << 8) + qs->class_lo;

    ngx_log_debug2(NGX_LOG_DEBUG_CORE, r->log, 0,
                   "resolver DNS response qt:%ui cl:%ui", qtype, qclass);

    if (qclass != 1) {
        ngx_log_error(r->log_level, r->log, 0,
                      "unknown query class %ui in DNS response", qclass);
        return;
    }

    switch (qtype) {

    case NGX_RESOLVE_A:

        ngx_resolver_process_a(r, buf, n, ident, code, nan,
                               i + sizeof(ngx_resolver_qs_t));

        break;

    case NGX_RESOLVE_PTR:

        ngx_resolver_process_ptr(r, buf, n, ident, code, nan);

        break;

    default:
        ngx_log_error(r->log_level, r->log, 0,
                      "unknown query type %ui in DNS response", qtype);
        return;
    }

    return;

short_response:

    err = "short dns response";

done: