ngx_resolver.c

Nginx是一个高性能的HTTP和反向代理服务器

static ngx_resolver_node_t *
ngx_resolver_lookup_addr(ngx_resolver_t *r, in_addr_t addr)
{
    ngx_rbtree_node_t  *node, *sentinel;

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

    while (node != sentinel) {

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

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

        /* addr == node->key */

        return (ngx_resolver_node_t *) node;
    }

    /* not found */

    return NULL;
}


static void
ngx_resolver_rbtree_insert_value(ngx_rbtree_node_t *temp,
    ngx_rbtree_node_t *node, ngx_rbtree_node_t *sentinel)
{
    size_t                 len;
    ngx_rbtree_node_t    **p;
    ngx_resolver_node_t   *rn, *rn_temp;

    for ( ;; ) {

        if (node->key < temp->key) {

            p = &temp->left;

        } else if (node->key > temp->key) {

            p = &temp->right;

        } else { /* node->key == temp->key */

            rn = (ngx_resolver_node_t *) node;
            rn_temp = (ngx_resolver_node_t *) temp;

            len = (rn->nlen > rn_temp->nlen) ? rn_temp->nlen : rn->nlen;

            p = (ngx_strncmp(rn->name, rn_temp->name, len) < 0)
                    ? &temp->left : &temp->right;
        }

        if (*p == sentinel) {
            break;
        }

        temp = *p;
    }

    *p = node;
    node->parent = temp;
    node->left = sentinel;
    node->right = sentinel;
    ngx_rbt_red(node);
}


static ngx_int_t
ngx_resolver_create_name_query(ngx_resolver_node_t *rn, ngx_resolver_ctx_t *ctx)
{
    u_char                *p, *s;
    size_t                 len;
    ngx_uint_t             ident;
    ngx_resolver_qs_t     *qs;
    ngx_resolver_query_t  *query;

    len = sizeof(ngx_resolver_query_t)
          + 1 + ctx->name.len + 1 + sizeof(ngx_resolver_qs_t);

    p = ngx_resolver_calloc(ctx->resolver, len);
    if (p == NULL) {
        return NGX_ERROR;
    }

    rn->qlen = (u_short) len;
    rn->query = p;

    query = (ngx_resolver_query_t *) p;

    ident = ngx_random();

    ngx_log_debug2(NGX_LOG_DEBUG_CORE, ctx->resolver->log, 0,
                   "resolve: \"%V\" %i", &ctx->name, ident & 0xffff);

    query->ident_hi = (u_char) ((ident >> 8) & 0xff);
    query->ident_lo = (u_char) (ident & 0xff);

    /* recursion query */
    query->flags_hi = 1; query->flags_lo = 0;

    /* one question */
    query->nqs_hi = 0; query->nqs_lo = 1;
    query->nan_hi = 0; query->nan_lo = 0;
    query->nns_hi = 0; query->nns_lo = 0;
    query->nar_hi = 0; query->nar_lo = 0;

    p += sizeof(ngx_resolver_query_t) + 1 + ctx->name.len + 1;

    qs = (ngx_resolver_qs_t *) p;

    /* query type */
    qs->type_hi = 0; qs->type_lo = (u_char) ctx->type;

    /* IP query class */
    qs->class_hi = 0; qs->class_lo = 1;

    /* convert "www.example.com" to "\3www\7example\3com\0" */

    len = 0;
    p--;
    *p-- = '\0';

    for (s = ctx->name.data + ctx->name.len - 1; s >= ctx->name.data; s--) {
        if (*s != '.') {
            *p = *s;
            len++;

        } else {
            if (len == 0) {
                return NGX_DECLINED;
            }

            *p = (u_char) len;
            len = 0;
        }

        p--;
    }

    *p = (u_char) len;

    return NGX_OK;
}


/* AF_INET only */

static ngx_int_t
ngx_resolver_create_addr_query(ngx_resolver_node_t *rn, ngx_resolver_ctx_t *ctx)
{
    u_char                *p, *d;
    size_t                 len;
    ngx_int_t              n;
    ngx_uint_t             ident;
    ngx_resolver_query_t  *query;

    len = sizeof(ngx_resolver_query_t)
          + sizeof(".255.255.255.255.in-addr.arpa.") - 1
          + sizeof(ngx_resolver_qs_t);

    p = ngx_resolver_calloc(ctx->resolver, len);
    if (p == NULL) {
        return NGX_ERROR;
    }

    rn->query = p;
    query = (ngx_resolver_query_t *) p;

    ident = ngx_random();

    query->ident_hi = (u_char) ((ident >> 8) & 0xff);
    query->ident_lo = (u_char) (ident & 0xff);

    /* recursion query */
    query->flags_hi = 1; query->flags_lo = 0;

    /* one question */
    query->nqs_hi = 0; query->nqs_lo = 1;
    query->nan_hi = 0; query->nan_lo = 0;
    query->nns_hi = 0; query->nns_lo = 0;
    query->nar_hi = 0; query->nar_lo = 0;

    p += sizeof(ngx_resolver_query_t);

    for (n = 0; n < 32; n += 8){
        d = ngx_sprintf(&p[1], "%ud", (ctx->addr >> n) & 0xff);
        *p = (u_char) (d - &p[1]);
        p = d;
    }

    /* query type "PTR", IP query class */
    ngx_memcpy(p, "\7in-addr\4arpa\0\0\14\0\1", 18);

    rn->qlen = (u_short)
                  (p + sizeof("\7in-addr\4arpa") + sizeof(ngx_resolver_qs_t)
                   - rn->query);

    return NGX_OK;
}


static ngx_int_t
ngx_resolver_copy(ngx_resolver_t *r, ngx_str_t *name, u_char *buf, u_char *src,
    u_char *last)
{
    char        *err;
    u_char      *p, *dst;
    ssize_t      len;
    ngx_uint_t   i, n;

    p = src;
    len = -1;

    /*
     * compression pointers allow to create endless loop, so we set limit;
     * 128 pointers should be enough to store 255-byte name
     */

    for (i = 0; i < 128; i++) {
        n = *p++;

        if (n == 0) {
            goto done;
        }

        if (n & 0xc0) {
            n = (n & 0x3f << 8) + *p;
            p = &buf[n];

        } else {
            len += 1 + n;
            p = &p[n];
        }

        if (p >= last) {
            err = "name is out of response";
            goto invalid;
        }
    }

    err = "compression pointers loop";

invalid:

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

    return NGX_ERROR;

done:

    if (name == NULL) {
        return NGX_OK;
    }

    dst = ngx_resolver_alloc(r, len);
    if (dst == NULL) {
        return NGX_ERROR;
    }

    name->data = dst;

    n = *src++;

    for ( ;; ) {
        if (n != 0xc0) {
            ngx_memcpy(dst, src, n);
            dst += n;
            src += n;

            n = *src++;

            if (n != 0) {
                *dst++ = '.';
            }

        } else {
            n = (n & 0x3f << 8) + *src;
            src = &buf[n];

            n = *src++;
        }

        if (n == 0) {
            name->len = dst - name->data;
            return NGX_OK;
        }
    }
}


static void
ngx_resolver_timeout_handler(ngx_event_t *ev)
{
    ngx_resolver_ctx_t  *ctx;

    ctx = ev->data;

    ctx->state = NGX_RESOLVE_TIMEDOUT;

    ctx->handler(ctx);
}


static void
ngx_resolver_free_node(ngx_resolver_t *r, ngx_resolver_node_t *rn)
{
    /* lock alloc mutex */

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

    if (rn->name) {
        ngx_resolver_free_locked(r, rn->name);
    }

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

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

    ngx_resolver_free_locked(r, rn);

    /* unlock alloc mutex */
}


static void *
ngx_resolver_alloc(ngx_resolver_t *r, size_t size)
{
    u_char  *p;

    /* lock alloc mutex */

    p = ngx_alloc(size, r->log);

    /* unlock alloc mutex */

    return p;
}


static void *
ngx_resolver_calloc(ngx_resolver_t *r, size_t size)
{
    u_char  *p;

    p = ngx_resolver_alloc(r, size);

    if (p) {
        ngx_memzero(p, size);
    }

    return p;
}


static void
ngx_resolver_free(ngx_resolver_t *r, void *p)
{
    /* lock alloc mutex */

    ngx_free(p);

    /* unlock alloc mutex */
}


static void
ngx_resolver_free_locked(ngx_resolver_t *r, void *p)
{
    ngx_free(p);
}


static void *
ngx_resolver_dup(ngx_resolver_t *r, void *src, size_t size)
{
    void  *dst;

    dst = ngx_resolver_alloc(r, size);

    if (dst == NULL) {
        return dst;
    }

    ngx_memcpy(dst, src, size);

    return dst;
}


char *
ngx_resolver_strerror(ngx_int_t err)
{
    static char *errors[] = {
        "Format error",     /* FORMERR */
        "Server failure",   /* SERVFAIL */
        "Host not found",   /* NXDOMAIN */
        "Unimplemented",    /* NOTIMP */
        "Operation refused" /* REFUSED */
    };

    if (err > 0 && err < 6) {
        return errors[err - 1];
    }

    if (err == NGX_RESOLVE_TIMEDOUT) {
        return "Operation timed out";
    }

    return "Unknown error";
}


ngx_int_t
ngx_udp_connect(ngx_udp_connection_t *uc)
{
    int                rc;
    ngx_int_t          event;
    ngx_event_t       *rev, *wev;
    ngx_socket_t       s;
    ngx_connection_t  *c;

    s = ngx_socket(AF_INET, SOCK_DGRAM, 0);

    ngx_log_debug1(NGX_LOG_DEBUG_EVENT, uc->log, 0, "UDP socket %d", s);

    if (s == -1) {
        ngx_log_error(NGX_LOG_ALERT, uc->log, ngx_socket_errno,
                      ngx_socket_n " failed");
        return NGX_ERROR;
    }

    c = ngx_get_connection(s, uc->log);

    if (c == NULL) {
        if (ngx_close_socket(s) == -1) {
            ngx_log_error(NGX_LOG_ALERT, uc->log, ngx_socket_errno,
                          ngx_close_socket_n "failed");
        }

        return NGX_ERROR;
    }

    if (ngx_nonblocking(s) == -1) {
        ngx_log_error(NGX_LOG_ALERT, uc->log, ngx_socket_errno,
                      ngx_nonblocking_n " failed");

        ngx_free_connection(c);

        if (ngx_close_socket(s) == -1) {
            ngx_log_error(NGX_LOG_ALERT, uc->log, ngx_socket_errno,
                          ngx_close_socket_n " failed");
        }

        return NGX_ERROR;
    }

    rev = c->read;
    wev = c->write;

    rev->log = uc->log;
    wev->log = uc->log;

    uc->connection = c;

    c->number = ngx_atomic_fetch_add(ngx_connection_counter, 1);

#if (NGX_THREADS)

    /* TODO: lock event when call completion handler */

    rev->lock = &c->lock;
    wev->lock = &c->lock;
    rev->own_lock = &c->lock;
    wev->own_lock = &c->lock;

#endif

    ngx_log_debug3(NGX_LOG_DEBUG_EVENT, uc->log, 0,
                   "connect to %V, fd:%d #%d", &uc->server, s, c->number);

    rc = connect(s, uc->sockaddr, uc->socklen);

    /* TODO: aio, iocp */

    if (rc == -1) {
        ngx_log_error(NGX_LOG_CRIT, uc->log, ngx_socket_errno,
                      "connect() to %V failed", &uc->server);

        return NGX_ERROR;
    }

    /* UDP sockets are always ready to write */
    wev->ready = 1;

    if (ngx_add_event) {

        event = (ngx_event_flags & NGX_USE_CLEAR_EVENT) ?
                    /* kqueue, epoll */                 NGX_CLEAR_EVENT:
                    /* select, poll, /dev/poll */       NGX_LEVEL_EVENT;
                    /* eventport event type has no meaning: oneshot only */

        if (ngx_add_event(rev, NGX_READ_EVENT, event) != NGX_OK) {
            return NGX_ERROR;
        }

    } else {
        /* rtsig */

        if (ngx_add_conn(c) == NGX_ERROR) {
            return NGX_ERROR;
        }
    }

    return NGX_OK;
}