nginx中域名解析

#if (NGX_HAVE_GETADDRINFO && NGX_HAVE_INET6)

ngx_int_t
ngx_inet_resolve_host(ngx_pool_t *pool, ngx_url_t *u)
{
    u_char               *p, *host;
    size_t                len;
    in_port_t             port;
    ngx_uint_t            i;
    struct addrinfo       hints, *res, *rp;
    struct sockaddr_in   *sin;
    struct sockaddr_in6  *sin6;

    port = htons(u->port);

    host = ngx_alloc(u->host.len + 1, pool->log);
    if (host == NULL) {
        return NGX_ERROR;
    }

    (void) ngx_cpystrn(host, u->host.data, u->host.len + 1);

    ngx_memzero(&hints, sizeof(struct addrinfo));
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
#ifdef AI_ADDRCONFIG
    hints.ai_flags = AI_ADDRCONFIG;
#endif

    if (getaddrinfo((char *) host, NULL, &hints, &res) != 0) {
        u->err = "host not found";
        ngx_free(host);
        return NGX_ERROR;
    }

    ngx_free(host);

    for (i = 0, rp = res; rp != NULL; rp = rp->ai_next) {

        switch (rp->ai_family) {

        case AF_INET:
        case AF_INET6:
            break;

        default:
            continue;
        }

        i++;
    }

    if (i == 0) {
        u->err = "host not found";
        goto failed;
    }

    /* MP: ngx_shared_palloc() */

    u->addrs = ngx_pcalloc(pool, i * sizeof(ngx_addr_t));
    if (u->addrs == NULL) {
        goto failed;
    }

    u->naddrs = i;

    i = 0;

    /* AF_INET addresses first */

    for (rp = res; rp != NULL; rp = rp->ai_next) {

        if (rp->ai_family != AF_INET) {
            continue;
        }

        sin = ngx_pcalloc(pool, rp->ai_addrlen);
        if (sin == NULL) {
            goto failed;
        }

        ngx_memcpy(sin, rp->ai_addr, rp->ai_addrlen);

        sin->sin_port = port;

        u->addrs[i].sockaddr = (struct sockaddr *) sin;
        u->addrs[i].socklen = rp->ai_addrlen;

        len = NGX_INET_ADDRSTRLEN + sizeof(":65535") - 1;

        p = ngx_pnalloc(pool, len);
        if (p == NULL) {
            goto failed;
        }

        len = ngx_sock_ntop((struct sockaddr *) sin, rp->ai_addrlen, p, len, 1);

        u->addrs[i].name.len = len;
        u->addrs[i].name.data = p;

        i++;
    }

    for (rp = res; rp != NULL; rp = rp->ai_next) {

        if (rp->ai_family != AF_INET6) {
            continue;
        }

        sin6 = ngx_pcalloc(pool, rp->ai_addrlen);
        if (sin6 == NULL) {
            goto failed;
        }

        ngx_memcpy(sin6, rp->ai_addr, rp->ai_addrlen);

        sin6->sin6_port = port;

        u->addrs[i].sockaddr = (struct sockaddr *) sin6;
        u->addrs[i].socklen = rp->ai_addrlen;

        len = NGX_INET6_ADDRSTRLEN + sizeof("[]:65535") - 1;

        p = ngx_pnalloc(pool, len);
        if (p == NULL) {
            goto failed;
        }

        len = ngx_sock_ntop((struct sockaddr *) sin6, rp->ai_addrlen, p,
                            len, 1);

        u->addrs[i].name.len = len;
        u->addrs[i].name.data = p;

        i++;
    }

    freeaddrinfo(res);
    return NGX_OK;

failed:

    freeaddrinfo(res);
    return NGX_ERROR;
}

#else /* !NGX_HAVE_GETADDRINFO || !NGX_HAVE_INET6 */

ngx_int_t
ngx_inet_resolve_host(ngx_pool_t *pool, ngx_url_t *u)
{
    u_char              *p, *host;
    size_t               len;
    in_port_t            port;
    in_addr_t            in_addr;
    ngx_uint_t           i;
    struct hostent      *h;
    struct sockaddr_in  *sin;

    /* AF_INET only */

    port = htons(u->port);

    in_addr = ngx_inet_addr(u->host.data, u->host.len);

    if (in_addr == INADDR_NONE) {
        host = ngx_alloc(u->host.len + 1, pool->log);
        if (host == NULL) {
            return NGX_ERROR;
        }

        (void) ngx_cpystrn(host, u->host.data, u->host.len + 1);

        h = gethostbyname((char *) host);

        ngx_free(host);

        if (h == NULL || h->h_addr_list[0] == NULL) {
            u->err = "host not found";
            return NGX_ERROR;
        }

        for (i = 0; h->h_addr_list[i] != NULL; i++) { /* void */ }

        /* MP: ngx_shared_palloc() */

        u->addrs = ngx_pcalloc(pool, i * sizeof(ngx_addr_t));
        if (u->addrs == NULL) {
            return NGX_ERROR;
        }

        u->naddrs = i;

        for (i = 0; i < u->naddrs; i++) {

            sin = ngx_pcalloc(pool, sizeof(struct sockaddr_in));
            if (sin == NULL) {
                return NGX_ERROR;
            }

            sin->sin_family = AF_INET;
            sin->sin_port = port;
            sin->sin_addr.s_addr = *(in_addr_t *) (h->h_addr_list[i]);

            u->addrs[i].sockaddr = (struct sockaddr *) sin;
            u->addrs[i].socklen = sizeof(struct sockaddr_in);

            len = NGX_INET_ADDRSTRLEN + sizeof(":65535") - 1;

            p = ngx_pnalloc(pool, len);
            if (p == NULL) {
                return NGX_ERROR;
            }

            len = ngx_sock_ntop((struct sockaddr *) sin,
                                sizeof(struct sockaddr_in), p, len, 1);

            u->addrs[i].name.len = len;
            u->addrs[i].name.data = p;
        }

    } else {

        /* MP: ngx_shared_palloc() */

        u->addrs = ngx_pcalloc(pool, sizeof(ngx_addr_t));
        if (u->addrs == NULL) {
            return NGX_ERROR;
        }

        sin = ngx_pcalloc(pool, sizeof(struct sockaddr_in));
        if (sin == NULL) {
            return NGX_ERROR;
        }

        u->naddrs = 1;

        sin->sin_family = AF_INET;
        sin->sin_port = port;
        sin->sin_addr.s_addr = in_addr;

        u->addrs[0].sockaddr = (struct sockaddr *) sin;
        u->addrs[0].socklen = sizeof(struct sockaddr_in);

        p = ngx_pnalloc(pool, u->host.len + sizeof(":65535") - 1);
        if (p == NULL) {
            return NGX_ERROR;
        }

        u->addrs[0].name.len = ngx_sprintf(p, "%V:%d",
                                           &u->host, ntohs(port)) - p;
        u->addrs[0].name.data = p;
    }

    return NGX_OK;
}

#endif /* NGX_HAVE_GETADDRINFO && NGX_HAVE_INET6 */