ngx_resolver.c

Nginx是一个高性能的HTTP和反向代理服务器

    ngx_log_error(r->log_level, r->log, 0, err);

    return;
}


static void
ngx_resolver_process_a(ngx_resolver_t *r, u_char *buf, size_t last,
    ngx_uint_t ident, ngx_uint_t code, ngx_uint_t nan, ngx_uint_t ans)
{
    char                 *err;
    u_char               *cname;
    size_t                len;
    uint32_t              hash;
    in_addr_t             addr, *addrs;
    ngx_str_t             name;
    ngx_uint_t            qtype, qident, naddrs, a, i, n, start;
    ngx_resolver_an_t    *an;
    ngx_resolver_ctx_t   *ctx, *next;
    ngx_resolver_node_t  *rn;

    if (ngx_resolver_copy(r, &name, buf, &buf[12], &buf[last]) != NGX_OK) {
        return;
    }

    ngx_log_debug1(NGX_LOG_DEBUG_CORE, r->log, 0, "resolver qs:%V", &name);

    hash = ngx_crc32_short(name.data, name.len);

    /* lock name mutex */

    rn = ngx_resolver_lookup_name(r, &name, hash);

    if (rn == NULL || rn->query == NULL) {
        ngx_log_error(r->log_level, r->log, 0,
                      "unexpected response for %V", &name);
        goto failed;
    }

    qident = (rn->query[0] << 8) + rn->query[1];

    if (ident != qident) {
        ngx_log_error(r->log_level, r->log, 0,
                      "wrong ident %ui response for %V, expect %ui",
                      ident, &name, qident);
        goto failed;
    }

    if (code == 0 && nan == 0) {
        code = 3; /* NXDOMAIN */
    }

    if (code) {
        next = rn->waiting;
        rn->waiting = NULL;

        ngx_queue_remove(&rn->queue);

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

        ngx_resolver_free_node(r, rn);

        /* unlock name mutex */

        while (next) {
             ctx = next;
             ctx->state = code;
             next = ctx->next;

             ctx->handler(ctx);
        }

        return;
    }

    i = ans;
    naddrs = 0;
    addr = 0;
    addrs = NULL;
    cname = NULL;
    qtype = 0;

    for (a = 0; a < nan; a++) {

        start = i;

        while (i < last) {

            if (buf[i] & 0xc0) {
                i += 2;
                goto found;
            }

            if (buf[i] == 0) {
                i++;
                goto test_length;
            }

            i += 1 + buf[i];
        }

        goto short_response;

    test_length:

        if (i - start < 2) {
            err = "invalid name in dns response";
            goto invalid;
        }

    found:

        if (i + sizeof(ngx_resolver_an_t) >= last) {
            goto short_response;
        }

        an = (ngx_resolver_an_t *) &buf[i];

        qtype = (an->type_hi << 8) + an->type_lo;
        len = (an->len_hi << 8) + an->len_lo;

        if (qtype == NGX_RESOLVE_A) {

            i += sizeof(ngx_resolver_an_t);

            if (i + len > last) {
                goto short_response;
            }

            addr = htonl((buf[i] << 24) + (buf[i + 1] << 16)
                         + (buf[i + 2] << 8) + (buf[i + 3]));

            naddrs++;

            i += len;

        } else if (qtype == NGX_RESOLVE_CNAME) {
            cname = &buf[i] + sizeof(ngx_resolver_an_t);
            i += sizeof(ngx_resolver_an_t) + len;

        } else if (qtype == NGX_RESOLVE_DNAME) {
            i += sizeof(ngx_resolver_an_t) + len;

        } else {
            ngx_log_error(r->log_level, r->log, 0,
                          "unexpected qtype %ui", qtype);
        }
    }

    ngx_log_debug2(NGX_LOG_DEBUG_CORE, r->log, 0,
                   "resolver naddrs:%ui cname:%p", naddrs, cname);

    if (naddrs) {

        if (naddrs == 1) {
            rn->u.addr = addr;

        } else {

            addrs = ngx_resolver_alloc(r, naddrs * sizeof(in_addr_t));
            if (addrs == NULL) {
                return;
            }

            n = 0;
            i = ans;

            for (a = 0; a < nan; a++) {

                for ( ;; ) {

                    if (buf[i] & 0xc0) {
                        i += 2;
                        goto ok;
                    }

                    if (buf[i] == 0) {
                        i++;
                        goto ok;
                    }

                    i += 1 + buf[i];
                }

            ok:

                an = (ngx_resolver_an_t *) &buf[i];

                qtype = (an->type_hi << 8) + an->type_lo;
                len = (an->len_hi << 8) + an->len_lo;

                i += sizeof(ngx_resolver_an_t);

                if (qtype == NGX_RESOLVE_A) {

                    addrs[n++] = htonl((buf[i] << 24) + (buf[i + 1] << 16)
                                       + (buf[i + 2] << 8) + (buf[i + 3]));

                    if (n == naddrs) {
                        break;
                    }
                }

                i += len;
            }

            rn->u.addrs = addrs;

            addrs = ngx_resolver_dup(r, rn->u.addrs,
                                     naddrs * sizeof(in_addr_t));
            if (addrs == NULL) {
                return;
            }
        }

        rn->naddrs = (u_short) naddrs;

        ngx_queue_remove(&rn->queue);

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

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

        next = rn->waiting;
        rn->waiting = NULL;

        /* unlock name mutex */

        while (next) {
             ctx = next;
             ctx->state = NGX_OK;
             ctx->naddrs = naddrs;
             ctx->addrs = (naddrs == 1) ? &ctx->addr : addrs;
             ctx->addr = addr;
             next = ctx->next;

             ctx->handler(ctx);
        }

        if (naddrs) {
            ngx_resolver_free(r, addrs);
        }

        return;

    } else if (cname) {

        /* CNAME only */

        if (ngx_resolver_copy(r, &name, buf, cname, &buf[last]) != NGX_OK) {
            return;
        }

        ngx_log_debug1(NGX_LOG_DEBUG_CORE, r->log, 0,
                       "resolver cname:\"%V\"", &name);

        ngx_queue_remove(&rn->queue);

        rn->cnlen = (u_short) name.len;
        rn->u.cname = name.data;
        rn->valid = ngx_time() + r->valid;
        rn->expire = ngx_time() + r->expire;

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

        ctx = rn->waiting;
        rn->waiting = NULL;

        if (ctx) {
            ctx->name = name;

            (void) ngx_resolve_name_locked(r, ctx);
        }

        return;
    }

    ngx_log_error(r->log_level, r->log, 0,
               "no A or CNAME types in DNS responses, unknown query type: %ui",
               qtype);
    return;

short_response:

    err = "short dns response";

invalid:

    /* unlock name mutex */

    ngx_log_error(r->log_level, r->log, 0, err);

    return;

failed:

    /* unlock name mutex */

    return;
}


static void
ngx_resolver_process_ptr(ngx_resolver_t *r, u_char *buf, size_t n,
    ngx_uint_t ident, ngx_uint_t code, ngx_uint_t nan)
{
    char                 *err;
    size_t                len;
    in_addr_t             addr;
    ngx_int_t             digit;
    ngx_str_t             name;
    ngx_uint_t            i, mask, qtype, qclass, qident;
    ngx_resolver_an_t    *an;
    ngx_resolver_ctx_t   *ctx, *next;
    ngx_resolver_node_t  *rn;

    if (ngx_resolver_copy(r, NULL, buf, &buf[12], &buf[n]) != NGX_OK) {
        goto invalid_in_addr_arpa;
    }

    addr = 0;
    i = 12;

    for (mask = 0; mask < 32; mask += 8) {
        len = buf[i++];

        digit = ngx_atoi(&buf[i], len);
        if (digit == NGX_ERROR || digit > 255) {
            goto invalid_in_addr_arpa;
        }

        addr += digit << mask;
        i += len;
    }

    if (ngx_strcmp(&buf[i], "\7in-addr\4arpa") != 0) {
        goto invalid_in_addr_arpa;
    }

    /* lock addr mutex */

    rn = ngx_resolver_lookup_addr(r, addr);

    if (rn == NULL || rn->query == NULL) {
        ngx_log_error(r->log_level, r->log, 0,
                      "unexpected response for %ud.%ud.%ud.%ud",
                      (addr >> 24) & 0xff, (addr >> 16) & 0xff,
                      (addr >> 8) & 0xff, addr & 0xff);
        goto failed;
    }

    qident = (rn->query[0] << 8) + rn->query[1];

    if (ident != qident) {
        ngx_log_error(r->log_level, r->log, 0,
                    "wrong ident %ui response for %ud.%ud.%ud.%ud, expect %ui",
                    ident, (addr >> 24) & 0xff, (addr >> 16) & 0xff,
                    (addr >> 8) & 0xff, addr & 0xff, qident);
        goto failed;
    }

    if (code == 0 && nan == 0) {
        code = 3; /* NXDOMAIN */
    }

    if (code) {
        next = rn->waiting;
        rn->waiting = NULL;

        ngx_queue_remove(&rn->queue);

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

        ngx_resolver_free_node(r, rn);

        /* unlock addr mutex */

        while (next) {
             ctx = next;
             ctx->state = code;
             next = ctx->next;

             ctx->handler(ctx);
        }

        return;
    }

    i += sizeof("\7in-addr\4arpa") + sizeof(ngx_resolver_qs_t);

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

    /* compression pointer to "XX.XX.XX.XX.in-addr.arpa */

    if (buf[i] != 0xc0 || buf[i + 1] != 0x0c) {
        err = "invalid in-addr.arpa name in DNS response";
        goto invalid;
    }

    an = (ngx_resolver_an_t *) &buf[i + 2];

    qtype = (an->type_hi << 8) + an->type_lo;
    qclass = (an->class_hi << 8) + an->class_lo;
    len = (an->len_hi << 8) + an->len_lo;

    ngx_log_debug3(NGX_LOG_DEBUG_CORE, r->log, 0,
                  "resolver qt:%ui cl:%ui len:%uz", qtype, qclass, len);

    i += 2 + sizeof(ngx_resolver_an_t);

    if (i + len > (ngx_uint_t) n) {
        goto short_response;
    }

    len -= 2;

    if (ngx_resolver_copy(r, &name, buf, &buf[i], &buf[n]) != NGX_OK) {
        return;
    }

    ngx_log_debug1(NGX_LOG_DEBUG_CORE, r->log, 0, "resolver an:%V", &name);

    if (len != (size_t) rn->nlen || ngx_strncmp(name.data, rn->name, len) != 0)
    {
        ngx_resolver_free(r, rn->name);
        rn->name = name.data;

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

    ngx_queue_remove(&rn->queue);

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

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

    next = rn->waiting;
    rn->waiting = NULL;

    /* unlock addr mutex */

    while (next) {
         ctx = next;
         ctx->state = NGX_OK;
         ctx->name = name;
         next = ctx->next;

         ctx->handler(ctx);
    }

    ngx_resolver_free(r, name.data);

    return;

invalid_in_addr_arpa:

    ngx_log_error(r->log_level, r->log, 0,
                  "invalid in-addr.arpa name in DNS response");
    return;

short_response:

    err = "short DNS response";

invalid:

    /* unlock addr mutex */

    ngx_log_error(r->log_level, r->log, 0, err);

    return;

failed:

    /* unlock addr mutex */

    return;
}


static ngx_resolver_node_t *
ngx_resolver_lookup_name(ngx_resolver_t *r, ngx_str_t *name, uint32_t hash)
{
    ngx_int_t             rc;
    size_t                len;
    ngx_rbtree_node_t    *node, *sentinel;
    ngx_resolver_node_t  *rn;

    node = r->name_rbtree.root;
    sentinel = r->name_rbtree.sentinel;

    while (node != sentinel) {

        if (hash < node->key) {
            node = node->left;
            continue;
        }

        if (hash > node->key) {
            node = node->right;
            continue;
        }

        /* hash == node->key */

        do {
            rn = (ngx_resolver_node_t *) node;

            len = (name->len > (size_t) rn->nlen) ? rn->nlen : name->len;

            rc = ngx_strncmp(name->data, rn->name, len);

            if (rc == 0) {
                return rn;
            }

            node = (rc < 0) ? node->left : node->right;

        } while (node != sentinel && hash == node->key);

        break;
    }

    /* not found */

    return NULL;
}