ngx_resolver.c

Nginx是一个高性能的HTTP和反向代理服务器

/*
 * Copyright (C) Igor Sysoev
 */


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


#define NGX_RESOLVER_UDP_SIZE   4096


typedef struct {
    u_char  ident_hi;
    u_char  ident_lo;
    u_char  flags_hi;
    u_char  flags_lo;
    u_char  nqs_hi;
    u_char  nqs_lo;
    u_char  nan_hi;
    u_char  nan_lo;
    u_char  nns_hi;
    u_char  nns_lo;
    u_char  nar_hi;
    u_char  nar_lo;
} ngx_resolver_query_t;


typedef struct {
    u_char  type_hi;
    u_char  type_lo;
    u_char  class_hi;
    u_char  class_lo;
} ngx_resolver_qs_t;


typedef struct {
    u_char  type_hi;
    u_char  type_lo;
    u_char  class_hi;
    u_char  class_lo;
    u_char  ttl[4];
    u_char  len_hi;
    u_char  len_lo;
} ngx_resolver_an_t;


ngx_int_t ngx_udp_connect(ngx_udp_connection_t *uc);


static void ngx_resolver_cleanup(void *data);
static void ngx_resolver_cleanup_tree(ngx_resolver_t *r, ngx_rbtree_t *tree);
static ngx_int_t ngx_resolve_name_locked(ngx_resolver_t *r,
    ngx_resolver_ctx_t *ctx);
static void ngx_resolver_expire(ngx_resolver_t *r, ngx_rbtree_t *tree,
    ngx_queue_t *queue);
static ngx_int_t ngx_resolver_send_query(ngx_resolver_t *r,
    ngx_resolver_node_t *rn);
static ngx_int_t ngx_resolver_create_name_query(ngx_resolver_node_t *rn,
    ngx_resolver_ctx_t *ctx);
static ngx_int_t ngx_resolver_create_addr_query(ngx_resolver_node_t *rn,
    ngx_resolver_ctx_t *ctx);
static void ngx_resolver_resend_handler(ngx_event_t *ev);
static time_t ngx_resolver_resend(ngx_resolver_t *r, ngx_rbtree_t *tree,
    ngx_queue_t *queue);
static void ngx_resolver_read_response(ngx_event_t *rev);
static void ngx_resolver_process_response(ngx_resolver_t *r, u_char *buf,
    size_t n);
static void ngx_resolver_process_a(ngx_resolver_t *r, u_char *buf, size_t n,
    ngx_uint_t ident, ngx_uint_t code, ngx_uint_t nan, ngx_uint_t ans);
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);
static ngx_resolver_node_t *ngx_resolver_lookup_name(ngx_resolver_t *r,
    ngx_str_t *name, uint32_t hash);
static ngx_resolver_node_t *ngx_resolver_lookup_addr(ngx_resolver_t *r,
    in_addr_t addr);
static void ngx_resolver_rbtree_insert_value(ngx_rbtree_node_t *temp,
    ngx_rbtree_node_t *node, ngx_rbtree_node_t *sentinel);
static ngx_int_t ngx_resolver_copy(ngx_resolver_t *r, ngx_str_t *name,
    u_char *buf, u_char *src, u_char *last);
static void ngx_resolver_timeout_handler(ngx_event_t *ev);
static void ngx_resolver_free_node(ngx_resolver_t *r, ngx_resolver_node_t *rn);
static void *ngx_resolver_alloc(ngx_resolver_t *r, size_t size);
static void *ngx_resolver_calloc(ngx_resolver_t *r, size_t size);
static void ngx_resolver_free(ngx_resolver_t *r, void *p);
static void ngx_resolver_free_locked(ngx_resolver_t *r, void *p);
static void *ngx_resolver_dup(ngx_resolver_t *r, void *src, size_t size);


/* STUB: ngx_peer_addr_t * */

ngx_resolver_t *
ngx_resolver_create(ngx_conf_t *cf, ngx_peer_addr_t *addr)
{
    ngx_resolver_t        *r;
    ngx_pool_cleanup_t    *cln;
    ngx_udp_connection_t  *uc;

    cln = ngx_pool_cleanup_add(cf->pool, 0);
    if (cln == NULL) {
        return NULL;
    }

    cln->handler = ngx_resolver_cleanup;

    r = ngx_calloc(sizeof(ngx_resolver_t), cf->log);
    if (r == NULL) {
        return NULL;
    }

    cln->data = r;

    r->event = ngx_calloc(sizeof(ngx_event_t), cf->log);
    if (r->event == NULL) {
        return NULL;
    }

    ngx_rbtree_init(&r->name_rbtree, &r->name_sentinel,
                    ngx_resolver_rbtree_insert_value);

    ngx_rbtree_init(&r->addr_rbtree, &r->addr_sentinel,
                    ngx_rbtree_insert_value);

    ngx_queue_init(&r->name_resend_queue);
    ngx_queue_init(&r->addr_resend_queue);

    ngx_queue_init(&r->name_expire_queue);
    ngx_queue_init(&r->addr_expire_queue);

    r->event->handler = ngx_resolver_resend_handler;
    r->event->data = r;
    r->event->log = cf->cycle->new_log;
    r->ident = -1;

    r->resend_timeout = 5;
    r->expire = 30;
    r->valid = 300;

    r->log = cf->cycle->new_log;
    r->log_level = NGX_LOG_ALERT;

    if (addr) {
        uc = ngx_calloc(sizeof(ngx_udp_connection_t), cf->log);
        if (uc == NULL) {
            return NULL;
        }

        r->udp_connection = uc;

        uc->sockaddr = addr->sockaddr;
        uc->socklen = addr->socklen;
        uc->server = addr->name;
        uc->log = cf->cycle->new_log;
    }

    return r;
}


static void
ngx_resolver_cleanup(void *data)
{
    ngx_resolver_t  *r = data;

    if (r) {
        ngx_log_debug0(NGX_LOG_DEBUG_CORE, ngx_cycle->log, 0,
                       "cleanup resolver");

        ngx_resolver_cleanup_tree(r, &r->name_rbtree);

        ngx_resolver_cleanup_tree(r, &r->addr_rbtree);

        if (r->event) {
            ngx_free(r->event);
        }

        if (r->udp_connection) {
            if (r->udp_connection->connection) {
                ngx_close_connection(r->udp_connection->connection);
            }

            ngx_free(r->udp_connection);
        }

        ngx_free(r);
    }
}


static void
ngx_resolver_cleanup_tree(ngx_resolver_t *r, ngx_rbtree_t *tree)
{
    ngx_resolver_ctx_t   *ctx, *next;
    ngx_resolver_node_t  *rn;

    while (tree->root != tree->sentinel) {

        rn = (ngx_resolver_node_t *) ngx_rbtree_min(tree->root, tree->sentinel);

        ngx_queue_remove(&rn->queue);

        for (ctx = rn->waiting; ctx; ctx = next) {
            next = ctx->next; 

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

            ngx_resolver_free(r, ctx);
        }

        ngx_rbtree_delete(tree, &rn->node);

        ngx_resolver_free_node(r, rn);
    }
}


ngx_resolver_ctx_t *
ngx_resolve_start(ngx_resolver_t *r, ngx_resolver_ctx_t *temp)
{
    in_addr_t            addr;
    ngx_resolver_ctx_t  *ctx;

    if (temp) {
        addr = ngx_inet_addr(temp->name.data, temp->name.len);

        if (addr != INADDR_NONE) {
            temp->resolver = r;
            temp->state = NGX_OK;
            temp->naddrs = 1;
            temp->addrs = &temp->addr;
            temp->addr = addr;
            temp->quick = 1;

            return temp;
        }
    }

    if (r->udp_connection == NULL) {
        return NGX_NO_RESOLVER;
    }

    ctx = ngx_resolver_calloc(r, sizeof(ngx_resolver_ctx_t));

    if (ctx) {
        ctx->resolver = r;
    }

    return ctx;
}


ngx_int_t
ngx_resolve_name(ngx_resolver_ctx_t *ctx)
{
    ngx_int_t        rc;
    ngx_resolver_t  *r;

    r = ctx->resolver;

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

    if (ctx->quick) {
        ctx->handler(ctx);
        return NGX_OK;
    }

    /* lock name mutex */

    rc = ngx_resolve_name_locked(r, ctx);

    if (rc == NGX_OK) {
        return NGX_OK;
    }

    /* unlock name mutex */

    if (rc == NGX_AGAIN) {
        return NGX_OK;
    }

    /* NGX_ERROR */

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

    ngx_resolver_free(r, ctx);

    return NGX_ERROR;
}


void
ngx_resolve_name_done(ngx_resolver_ctx_t *ctx)
{
    uint32_t              hash;
    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 name done: %i", ctx->state);

    if (ctx->quick) {
        return;
    }

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

    /* lock name mutex */

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

        hash = ngx_crc32_short(ctx->name.data, ctx->name.len);

        rn = ngx_resolver_lookup_name(r, &ctx->name, hash);

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

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

                    goto done;
                }

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

        ngx_log_error(NGX_LOG_ALERT, r->log, 0,
                      "could not cancel %V resolving", &ctx->name);
    }

done:

    ngx_resolver_expire(r, &r->name_rbtree, &r->name_expire_queue);

    /* unlock name mutex */

    /* lock alloc mutex */

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

    ngx_resolver_free_locked(r, ctx);

    /* unlock alloc mutex */
}


/* NGX_RESOLVE_A only */

static ngx_int_t
ngx_resolve_name_locked(ngx_resolver_t *r, ngx_resolver_ctx_t *ctx)
{
    uint32_t              hash;
    in_addr_t             addr, *addrs;
    ngx_int_t             rc;
    ngx_uint_t            naddrs;
    ngx_resolver_ctx_t   *next;
    ngx_resolver_node_t  *rn;

    hash = ngx_crc32_short(ctx->name.data, ctx->name.len);

    rn = ngx_resolver_lookup_name(r, &ctx->name, hash);

    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->name_expire_queue, &rn->queue);

            naddrs = rn->naddrs;

            if (naddrs) {

                /* NGX_RESOLVE_A answer */

                if (naddrs != 1) {
                    addr = 0;
                    addrs = ngx_resolver_dup(r, rn->u.addrs,
                                             naddrs * sizeof(in_addr_t));
                    if (addrs == NULL) {
                        return NGX_ERROR;
                    }

                } else {
                    addr = rn->u.addr;
                    addrs = NULL;
                }

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

                /* unlock name mutex */

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

                    ctx->handler(ctx);

                    ctx = next;
                } while (ctx);

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

                return NGX_OK;
            }

            /* NGX_RESOLVE_CNAME */

            if (ctx->recursion++ < NGX_RESOLVER_MAX_RECURSION) {

                ctx->name.len = rn->cnlen;
                ctx->name.data = rn->u.cname;

                return ngx_resolve_name_locked(r, ctx);
            }

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

            /* unlock name mutex */

            do {
                ctx->state = NGX_RESOLVE_NXDOMAIN;
                next = ctx->next;

                ctx->handler(ctx);

                ctx = next;
            } while (ctx);

            return NGX_OK;
        }

        if (rn->waiting) {

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

            return NGX_AGAIN;
        }

        ngx_queue_remove(&rn->queue);

        /* lock alloc mutex */

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

        if (rn->cnlen) {
            ngx_resolver_free_locked(r, rn->u.cname);
        }

        if (rn->naddrs > 1) {
            ngx_resolver_free_locked(r, rn->u.addrs);
        }

        /* unlock alloc mutex */

    } else {

        rn = ngx_resolver_alloc(r, sizeof(ngx_resolver_node_t));
        if (rn == NULL) {
            return NGX_ERROR;
        }

        rn->name = ngx_resolver_dup(r, ctx->name.data, ctx->name.len);
        if (rn->name == NULL) {
            ngx_resolver_free(r, rn);
            return NGX_ERROR;
        }

        rn->node.key = hash;
        rn->nlen = (u_short) ctx->name.len;
        rn->query = NULL;

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

    rc = ngx_resolver_create_name_query(rn, ctx);

    if (rc == NGX_ERROR) {
        goto failed;
    }

    if (rc == NGX_DECLINED) {
        ngx_rbtree_delete(&r->name_rbtree, &rn->node);

        ngx_resolver_free(r, rn->query);
        ngx_resolver_free(r, rn->name);
        ngx_resolver_free(r, rn);

        ctx->state = NGX_RESOLVE_NXDOMAIN;
        ctx->handler(ctx);

        return NGX_OK;
    }

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

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