libsystemd-dns: merge into libsystemd

Also rename sd-dns -> sd-resolv.

1 files changed, 1158 insertions, 0 deletions

diff --git a/src/libsystemd/sd-resolv.c b/src/libsystemd/sd-resolv.c
new file mode 100644
index 0000000000..2db66eb2ff
--- /dev/null
+++ b/src/libsystemd/sd-resolv.c
@@ -0,0 +1,1158 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2005-2008 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <assert.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <unistd.h>
+#include <sys/select.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <sys/wait.h>
+#include <sys/types.h>
+#include <pwd.h>
+#include <netinet/in.h>
+#include <arpa/nameser.h>
+#include <resolv.h>
+#include <dirent.h>
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <stdint.h>
+#include <pthread.h>
+#include <sys/prctl.h>
+
+#include "sd-resolv.h"
+#include "util.h"
+
+#define MAX_WORKERS 16
+#define MAX_QUERIES 256
+#define BUFSIZE (10240)
+
+typedef enum {
+        REQUEST_ADDRINFO,
+        RESPONSE_ADDRINFO,
+        REQUEST_NAMEINFO,
+        RESPONSE_NAMEINFO,
+        REQUEST_RES_QUERY,
+        REQUEST_RES_SEARCH,
+        RESPONSE_RES,
+        REQUEST_TERMINATE,
+        RESPONSE_DIED
+} query_type_t;
+
+enum {
+        REQUEST_RECV_FD = 0,
+        REQUEST_SEND_FD = 1,
+        RESPONSE_RECV_FD = 2,
+        RESPONSE_SEND_FD = 3,
+        MESSAGE_FD_MAX = 4
+};
+
+struct asyncns {
+        int fds[MESSAGE_FD_MAX];
+
+        pthread_t workers[MAX_WORKERS];
+        unsigned valid_workers;
+
+        unsigned current_id, current_index;
+        asyncns_query_t* queries[MAX_QUERIES];
+
+        asyncns_query_t *done_head, *done_tail;
+
+        int n_queries;
+        int dead;
+};
+
+struct asyncns_query {
+        asyncns_t *asyncns;
+        int done;
+        unsigned id;
+        query_type_t type;
+        asyncns_query_t *done_next, *done_prev;
+        int ret;
+        int _errno;
+        int _h_errno;
+        struct addrinfo *addrinfo;
+        char *serv, *host;
+        void *userdata;
+};
+
+typedef struct rheader {
+        query_type_t type;
+        unsigned id;
+        size_t length;
+} rheader_t;
+
+typedef struct addrinfo_request {
+        struct rheader header;
+        int hints_is_null;
+        int ai_flags;
+        int ai_family;
+        int ai_socktype;
+        int ai_protocol;
+        size_t node_len, service_len;
+} addrinfo_request_t;
+
+typedef struct addrinfo_response {
+        struct rheader header;
+        int ret;
+        int _errno;
+        int _h_errno;
+        /* followed by addrinfo_serialization[] */
+} addrinfo_response_t;
+
+typedef struct addrinfo_serialization {
+        int ai_flags;
+        int ai_family;
+        int ai_socktype;
+        int ai_protocol;
+        size_t ai_addrlen;
+        size_t canonname_len;
+        /* Followed by ai_addr amd ai_canonname with variable lengths */
+} addrinfo_serialization_t;
+
+typedef struct nameinfo_request {
+        struct rheader header;
+        int flags;
+        socklen_t sockaddr_len;
+        int gethost, getserv;
+} nameinfo_request_t;
+
+typedef struct nameinfo_response {
+        struct rheader header;
+        size_t hostlen, servlen;
+        int ret;
+        int _errno;
+        int _h_errno;
+} nameinfo_response_t;
+
+typedef struct res_request {
+        struct rheader header;
+        int class;
+        int type;
+        size_t dname_len;
+} res_request_t;
+
+typedef struct res_response {
+        struct rheader header;
+        int ret;
+        int _errno;
+        int _h_errno;
+} res_response_t;
+
+typedef union packet {
+        rheader_t rheader;
+        addrinfo_request_t addrinfo_request;
+        addrinfo_response_t addrinfo_response;
+        nameinfo_request_t nameinfo_request;
+        nameinfo_response_t nameinfo_response;
+        res_request_t res_request;
+        res_response_t res_response;
+} packet_t;
+
+static int send_died(int out_fd) {
+        rheader_t rh = {};
+        assert(out_fd > 0);
+
+        rh.type = RESPONSE_DIED;
+        rh.id = 0;
+        rh.length = sizeof(rh);
+
+        return send(out_fd, &rh, rh.length, MSG_NOSIGNAL);
+}
+
+static void *serialize_addrinfo(void *p, const struct addrinfo *ai, size_t *length, size_t maxlength) {
+        addrinfo_serialization_t s;
+        size_t cnl, l;
+        assert(p);
+        assert(ai);
+        assert(length);
+        assert(*length <= maxlength);
+
+        cnl = (ai->ai_canonname ? strlen(ai->ai_canonname)+1 : 0);
+        l = sizeof(addrinfo_serialization_t) + ai->ai_addrlen + cnl;
+
+        if (*length + l > maxlength)
+                return NULL;
+
+        s.ai_flags = ai->ai_flags;
+        s.ai_family = ai->ai_family;
+        s.ai_socktype = ai->ai_socktype;
+        s.ai_protocol = ai->ai_protocol;
+        s.ai_addrlen = ai->ai_addrlen;
+        s.canonname_len = cnl;
+
+        memcpy((uint8_t*) p, &s, sizeof(addrinfo_serialization_t));
+        memcpy((uint8_t*) p + sizeof(addrinfo_serialization_t), ai->ai_addr, ai->ai_addrlen);
+
+        if (ai->ai_canonname)
+                strcpy((char*) p + sizeof(addrinfo_serialization_t) + ai->ai_addrlen, ai->ai_canonname);
+
+        *length += l;
+        return (uint8_t*) p + l;
+}
+
+static int send_addrinfo_reply(int out_fd, unsigned id, int ret, struct addrinfo *ai, int _errno, int _h_errno) {
+        addrinfo_response_t data[BUFSIZE/sizeof(addrinfo_response_t) + 1] = {};
+        addrinfo_response_t *resp = data;
+        assert(out_fd >= 0);
+
+        resp->header.type = RESPONSE_ADDRINFO;
+        resp->header.id = id;
+        resp->header.length = sizeof(addrinfo_response_t);
+        resp->ret = ret;
+        resp->_errno = _errno;
+        resp->_h_errno = _h_errno;
+
+        if (ret == 0 && ai) {
+                void *p = data + 1;
+                struct addrinfo *k;
+
+                for (k = ai; k; k = k->ai_next) {
+                        p = serialize_addrinfo(p, k, &resp->header.length, (char*) data + BUFSIZE - (char*) p);
+                        if (!p) {
+                                resp->ret = EAI_MEMORY;
+                                break;
+                        }
+                }
+        }
+
+        if (ai)
+                freeaddrinfo(ai);
+
+        return send(out_fd, resp, resp->header.length, MSG_NOSIGNAL);
+}
+
+static int send_nameinfo_reply(int out_fd, unsigned id, int ret, const char *host, const char *serv, int _errno, int _h_errno) {
+        nameinfo_response_t data[BUFSIZE/sizeof(nameinfo_response_t) + 1] = {};
+        size_t hl, sl;
+        nameinfo_response_t *resp = data;
+
+        assert(out_fd >= 0);
+
+        sl = serv ? strlen(serv)+1 : 0;
+        hl = host ? strlen(host)+1 : 0;
+
+        resp->header.type = RESPONSE_NAMEINFO;
+        resp->header.id = id;
+        resp->header.length = sizeof(nameinfo_response_t) + hl + sl;
+        resp->ret = ret;
+        resp->_errno = _errno;
+        resp->_h_errno = _h_errno;
+        resp->hostlen = hl;
+        resp->servlen = sl;
+
+        assert(sizeof(data) >= resp->header.length);
+
+        if (host)
+                memcpy((uint8_t *)data + sizeof(nameinfo_response_t), host, hl);
+
+        if (serv)
+                memcpy((uint8_t *)data + sizeof(nameinfo_response_t) + hl, serv, sl);
+
+        return send(out_fd, resp, resp->header.length, MSG_NOSIGNAL);
+}
+
+static int send_res_reply(int out_fd, unsigned id, const unsigned char *answer, int ret, int _errno, int _h_errno) {
+        res_response_t data[BUFSIZE/sizeof(res_response_t) + 1] = {};
+        res_response_t *resp = data;
+
+        assert(out_fd >= 0);
+
+        resp->header.type = RESPONSE_RES;
+        resp->header.id = id;
+        resp->header.length = sizeof(res_response_t) + (ret < 0 ? 0 : ret);
+        resp->ret = ret;
+        resp->_errno = _errno;
+        resp->_h_errno = _h_errno;
+
+        assert(sizeof(data) >= resp->header.length);
+
+        if (ret > 0)
+                memcpy((uint8_t *)data + sizeof(res_response_t), answer, ret);
+
+        return send(out_fd, resp, resp->header.length, MSG_NOSIGNAL);
+}
+
+static int handle_request(int out_fd, const packet_t *packet, size_t length) {
+        const rheader_t *req;
+        assert(out_fd >= 0);
+
+        req = &packet->rheader;
+        assert(req);
+        assert(length >= sizeof(rheader_t));
+        assert(length == req->length);
+
+        switch (req->type) {
+        case REQUEST_ADDRINFO: {
+               struct addrinfo ai = {}, *result = NULL;
+               const addrinfo_request_t *ai_req = &packet->addrinfo_request;
+               const char *node, *service;
+               int ret;
+
+               assert(length >= sizeof(addrinfo_request_t));
+               assert(length == sizeof(addrinfo_request_t) + ai_req->node_len + ai_req->service_len);
+
+               ai.ai_flags = ai_req->ai_flags;
+               ai.ai_family = ai_req->ai_family;
+               ai.ai_socktype = ai_req->ai_socktype;
+               ai.ai_protocol = ai_req->ai_protocol;
+
+               node = ai_req->node_len ? (const char*) ai_req + sizeof(addrinfo_request_t) : NULL;
+               service = ai_req->service_len ? (const char*) ai_req + sizeof(addrinfo_request_t) + ai_req->node_len : NULL;
+
+               ret = getaddrinfo(node, service,
+                               ai_req->hints_is_null ? NULL : &ai,
+                               &result);
+
+               /* send_addrinfo_reply() frees result */
+               return send_addrinfo_reply(out_fd, req->id, ret, result, errno, h_errno);
+        }
+
+        case REQUEST_NAMEINFO: {
+               int ret;
+               const nameinfo_request_t *ni_req = &packet->nameinfo_request;
+               char hostbuf[NI_MAXHOST], servbuf[NI_MAXSERV];
+               struct sockaddr_storage sa;
+
+               assert(length >= sizeof(nameinfo_request_t));
+               assert(length == sizeof(nameinfo_request_t) + ni_req->sockaddr_len);
+
+               memcpy(&sa, (const uint8_t *) ni_req + sizeof(nameinfo_request_t), ni_req->sockaddr_len);
+
+               ret = getnameinfo((struct sockaddr *)&sa, ni_req->sockaddr_len,
+                               ni_req->gethost ? hostbuf : NULL, ni_req->gethost ? sizeof(hostbuf) : 0,
+                               ni_req->getserv ? servbuf : NULL, ni_req->getserv ? sizeof(servbuf) : 0,
+                               ni_req->flags);
+
+               return send_nameinfo_reply(out_fd, req->id, ret,
+                               ret == 0 && ni_req->gethost ? hostbuf : NULL,
+                               ret == 0 && ni_req->getserv ? servbuf : NULL,
+                               errno, h_errno);
+        }
+
+        case REQUEST_RES_QUERY:
+        case REQUEST_RES_SEARCH: {
+                 int ret;
+                 HEADER answer[BUFSIZE/sizeof(HEADER) + 1];
+                 const res_request_t *res_req = &packet->res_request;
+                 const char *dname;
+
+                 assert(length >= sizeof(res_request_t));
+                 assert(length == sizeof(res_request_t) + res_req->dname_len);
+
+                 dname = (const char *) req + sizeof(res_request_t);
+
+                 if (req->type == REQUEST_RES_QUERY)
+                         ret = res_query(dname, res_req->class, res_req->type, (unsigned char *) answer, BUFSIZE);
+                 else
+                         ret = res_search(dname, res_req->class, res_req->type, (unsigned char *) answer, BUFSIZE);
+
+                 return send_res_reply(out_fd, req->id, (unsigned char *) answer, ret, errno, h_errno);
+        }
+
+        case REQUEST_TERMINATE:
+                 /* Quit */
+                 return -1;
+
+        default:
+                 ;
+        }
+
+        return 0;
+}
+
+static void* thread_worker(void *p) {
+        asyncns_t *asyncns = p;
+        sigset_t fullset;
+
+        /* No signals in this thread please */
+        sigfillset(&fullset);
+        pthread_sigmask(SIG_BLOCK, &fullset, NULL);
+
+        while (!asyncns->dead) {
+                packet_t buf[BUFSIZE/sizeof(packet_t) + 1];
+                ssize_t length;
+
+                length = recv(asyncns->fds[REQUEST_RECV_FD], buf, sizeof(buf), 0);
+
+                if (length <= 0) {
+                        if (length < 0 && (errno == EAGAIN || errno == EINTR))
+                                continue;
+                        break;
+                }
+
+                if (asyncns->dead)
+                        break;
+
+                if (handle_request(asyncns->fds[RESPONSE_SEND_FD], buf, (size_t) length) < 0)
+                        break;
+        }
+
+        send_died(asyncns->fds[RESPONSE_SEND_FD]);
+
+        return NULL;
+}
+
+asyncns_t* asyncns_new(unsigned n_proc) {
+        int i;
+        asyncns_t *asyncns = NULL;
+
+        assert(n_proc >= 1);
+
+        if (n_proc > MAX_WORKERS)
+                n_proc = MAX_WORKERS;
+
+        asyncns = malloc(sizeof(asyncns_t));
+        if (!asyncns) {
+                errno = ENOMEM;
+                goto fail;
+        }
+
+        asyncns->dead = 0;
+        asyncns->valid_workers = 0;
+
+        for (i = 0; i < MESSAGE_FD_MAX; i++)
+                asyncns->fds[i] = -1;
+
+        memset(asyncns->queries, 0, sizeof(asyncns->queries));
+
+#ifdef SOCK_CLOEXEC
+        if (socketpair(PF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0, asyncns->fds) < 0 ||
+                        socketpair(PF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0, asyncns->fds+2) < 0) {
+
+                /* Try again, without SOCK_CLOEXEC */
+                if (errno == EINVAL) {
+#endif
+                        if (socketpair(PF_UNIX, SOCK_DGRAM, 0, asyncns->fds) < 0 ||
+                                        socketpair(PF_UNIX, SOCK_DGRAM, 0, asyncns->fds+2) < 0)
+                                goto fail;
+#ifdef SOCK_CLOEXEC
+                } else
+                        goto fail;
+        }
+#endif
+
+        for (i = 0; i < MESSAGE_FD_MAX; i++)
+                fd_cloexec(asyncns->fds[i], true);
+
+        for (asyncns->valid_workers = 0; asyncns->valid_workers < n_proc; asyncns->valid_workers++) {
+                int r;
+                r = pthread_create(&asyncns->workers[asyncns->valid_workers], NULL, thread_worker, asyncns);
+                if (r) {
+                        errno = r;
+                        goto fail;
+                }
+        }
+
+        asyncns->current_index = asyncns->current_id = 0;
+        asyncns->done_head = asyncns->done_tail = NULL;
+        asyncns->n_queries = 0;
+
+        fd_nonblock(asyncns->fds[RESPONSE_RECV_FD], true);
+
+        return asyncns;
+
+fail:
+        if (asyncns)
+                asyncns_free(asyncns);
+
+        return NULL;
+}
+
+void asyncns_free(asyncns_t *asyncns) {
+        int i;
+        int saved_errno = errno;
+        unsigned p;
+
+        assert(asyncns);
+
+        asyncns->dead = 1;
+
+        if (asyncns->fds[REQUEST_SEND_FD] >= 0) {
+                rheader_t req = {};
+
+                req.type = REQUEST_TERMINATE;
+                req.length = sizeof(req);
+                req.id = 0;
+
+                /* Send one termination packet for each worker */
+                for (p = 0; p < asyncns->valid_workers; p++)
+                        send(asyncns->fds[REQUEST_SEND_FD], &req, req.length, MSG_NOSIGNAL);
+        }
+
+        /* Now terminate them and wait until they are gone. */
+        for (p = 0; p < asyncns->valid_workers; p++) {
+                for (;;) {
+                        if (pthread_join(asyncns->workers[p], NULL) != EINTR)
+                                break;
+                }
+        }
+
+        /* Close all communication channels */
+        for (i = 0; i < MESSAGE_FD_MAX; i++)
+                if (asyncns->fds[i] >= 0)
+                        close(asyncns->fds[i]);
+
+        for (p = 0; p < MAX_QUERIES; p++)
+                if (asyncns->queries[p])
+                        asyncns_cancel(asyncns, asyncns->queries[p]);
+
+        free(asyncns);
+
+        errno = saved_errno;
+}
+
+int asyncns_fd(asyncns_t *asyncns) {
+        assert(asyncns);
+
+        return asyncns->fds[RESPONSE_RECV_FD];
+}
+
+static asyncns_query_t *lookup_query(asyncns_t *asyncns, unsigned id) {
+        asyncns_query_t *q;
+        assert(asyncns);
+
+        q = asyncns->queries[id % MAX_QUERIES];
+        if (q)
+                if (q->id == id)
+                        return q;
+
+        return NULL;
+}
+
+static void complete_query(asyncns_t *asyncns, asyncns_query_t *q) {
+        assert(asyncns);
+        assert(q);
+        assert(!q->done);
+
+        q->done = 1;
+
+        if ((q->done_prev = asyncns->done_tail))
+                asyncns->done_tail->done_next = q;
+        else
+                asyncns->done_head = q;
+
+        asyncns->done_tail = q;
+        q->done_next = NULL;
+}
+
+static const void *unserialize_addrinfo(const void *p, struct addrinfo **ret_ai, size_t *length) {
+        addrinfo_serialization_t s;
+        size_t l;
+        struct addrinfo *ai;
+        assert(p);
+        assert(ret_ai);
+        assert(length);
+
+        if (*length < sizeof(addrinfo_serialization_t))
+                return NULL;
+
+        memcpy(&s, p, sizeof(s));
+
+        l = sizeof(addrinfo_serialization_t) + s.ai_addrlen + s.canonname_len;
+        if (*length < l)
+                return NULL;
+
+        ai = malloc(sizeof(struct addrinfo));
+        if (!ai)
+                goto fail;
+
+        ai->ai_addr = NULL;
+        ai->ai_canonname = NULL;
+        ai->ai_next = NULL;
+
+        if (s.ai_addrlen && !(ai->ai_addr = malloc(s.ai_addrlen)))
+                goto fail;
+
+        if (s.canonname_len && !(ai->ai_canonname = malloc(s.canonname_len)))
+                goto fail;
+
+        ai->ai_flags = s.ai_flags;
+        ai->ai_family = s.ai_family;
+        ai->ai_socktype = s.ai_socktype;
+        ai->ai_protocol = s.ai_protocol;
+        ai->ai_addrlen = s.ai_addrlen;
+
+        if (ai->ai_addr)
+                memcpy(ai->ai_addr, (const uint8_t*) p + sizeof(addrinfo_serialization_t), s.ai_addrlen);
+
+        if (ai->ai_canonname)
+                memcpy(ai->ai_canonname, (const uint8_t*) p + sizeof(addrinfo_serialization_t) + s.ai_addrlen, s.canonname_len);
+
+        *length -= l;
+        *ret_ai = ai;
+
+        return (const uint8_t*) p + l;
+
+
+fail:
+        if (ai)
+                asyncns_freeaddrinfo(ai);
+
+        return NULL;
+}
+
+static int handle_response(asyncns_t *asyncns, const packet_t *packet, size_t length) {
+        const rheader_t *resp;
+        asyncns_query_t *q;
+
+        assert(asyncns);
+
+        resp = &packet->rheader;
+        assert(resp);
+        assert(length >= sizeof(rheader_t));
+        assert(length == resp->length);
+
+        if (resp->type == RESPONSE_DIED) {
+                asyncns->dead = 1;
+                return 0;
+        }
+
+        q = lookup_query(asyncns, resp->id);
+        if (!q)
+                return 0;
+
+        switch (resp->type) {
+        case RESPONSE_ADDRINFO: {
+                const addrinfo_response_t *ai_resp = &packet->addrinfo_response;
+                const void *p;
+                size_t l;
+                struct addrinfo *prev = NULL;
+
+                assert(length >= sizeof(addrinfo_response_t));
+                assert(q->type == REQUEST_ADDRINFO);
+
+                q->ret = ai_resp->ret;
+                q->_errno = ai_resp->_errno;
+                q->_h_errno = ai_resp->_h_errno;
+                l = length - sizeof(addrinfo_response_t);
+                p = (const uint8_t*) resp + sizeof(addrinfo_response_t);
+
+                while (l > 0 && p) {
+                        struct addrinfo *ai = NULL;
+                        p = unserialize_addrinfo(p, &ai, &l);
+
+                        if (!p || !ai) {
+                                q->ret = EAI_MEMORY;
+                                break;
+                        }
+
+                        if (prev)
+                                prev->ai_next = ai;
+                        else
+                                q->addrinfo = ai;
+
+                        prev = ai;
+                }
+
+                complete_query(asyncns, q);
+                break;
+        }
+
+        case RESPONSE_NAMEINFO: {
+                const nameinfo_response_t *ni_resp = &packet->nameinfo_response;
+
+                assert(length >= sizeof(nameinfo_response_t));
+                assert(q->type == REQUEST_NAMEINFO);
+
+                q->ret = ni_resp->ret;
+                q->_errno = ni_resp->_errno;
+                q->_h_errno = ni_resp->_h_errno;
+
+                if (ni_resp->hostlen)
+                        if (!(q->host = strndup((const char*) ni_resp + sizeof(nameinfo_response_t), ni_resp->hostlen-1)))
+                                q->ret = EAI_MEMORY;
+
+                if (ni_resp->servlen)
+                        if (!(q->serv = strndup((const char*) ni_resp + sizeof(nameinfo_response_t) + ni_resp->hostlen, ni_resp->servlen-1)))
+                                q->ret = EAI_MEMORY;
+
+                complete_query(asyncns, q);
+                break;
+        }
+
+        case RESPONSE_RES: {
+                const res_response_t *res_resp = &packet->res_response;
+
+                assert(length >= sizeof(res_response_t));
+                assert(q->type == REQUEST_RES_QUERY || q->type == REQUEST_RES_SEARCH);
+
+                q->ret = res_resp->ret;
+                q->_errno = res_resp->_errno;
+                q->_h_errno = res_resp->_h_errno;
+
+                if (res_resp->ret >= 0)  {
+                        if (!(q->serv = malloc(res_resp->ret))) {
+                                q->ret = -1;
+                                q->_errno = ENOMEM;
+                        } else
+                                memcpy(q->serv, (const char *)resp + sizeof(res_response_t), res_resp->ret);
+                }
+
+                complete_query(asyncns, q);
+                break;
+        }
+
+        default:
+                ;
+        }
+
+        return 0;
+}
+
+int asyncns_wait(asyncns_t *asyncns, int block) {
+        int handled = 0;
+        assert(asyncns);
+
+        for (;;) {
+                packet_t buf[BUFSIZE/sizeof(packet_t) + 1];
+                ssize_t l;
+
+                if (asyncns->dead) {
+                        errno = ECHILD;
+                        return -1;
+                }
+
+                l = recv(asyncns->fds[RESPONSE_RECV_FD], buf, sizeof(buf), 0);
+                if (l < 0) {
+                        fd_set fds;
+
+                        if (errno != EAGAIN)
+                                return -1;
+
+                        if (!block || handled)
+                                return 0;
+
+                        FD_ZERO(&fds);
+                        FD_SET(asyncns->fds[RESPONSE_RECV_FD], &fds);
+
+                        if (select(asyncns->fds[RESPONSE_RECV_FD]+1, &fds, NULL, NULL, NULL) < 0)
+                                return -1;
+
+                        continue;
+                }
+
+                if (handle_response(asyncns, buf, (size_t) l) < 0)
+                        return -1;
+
+                handled = 1;
+        }
+}
+
+static asyncns_query_t *alloc_query(asyncns_t *asyncns) {
+        asyncns_query_t *q;
+        assert(asyncns);
+
+        if (asyncns->n_queries >= MAX_QUERIES) {
+                errno = ENOMEM;
+                return NULL;
+        }
+
+        while (asyncns->queries[asyncns->current_index]) {
+                asyncns->current_index++;
+                asyncns->current_id++;
+
+                while (asyncns->current_index >= MAX_QUERIES)
+                        asyncns->current_index -= MAX_QUERIES;
+        }
+
+        q = asyncns->queries[asyncns->current_index] = malloc(sizeof(asyncns_query_t));
+        if (!q) {
+                errno = ENOMEM;
+                return NULL;
+        }
+
+        asyncns->n_queries++;
+
+        q->asyncns = asyncns;
+        q->done = 0;
+        q->id = asyncns->current_id;
+        q->done_next = q->done_prev = NULL;
+        q->ret = 0;
+        q->_errno = 0;
+        q->_h_errno = 0;
+        q->addrinfo = NULL;
+        q->userdata = NULL;
+        q->host = q->serv = NULL;
+
+        return q;
+}
+
+asyncns_query_t* asyncns_getaddrinfo(asyncns_t *asyncns, const char *node, const char *service, const struct addrinfo *hints) {
+        addrinfo_request_t data[BUFSIZE/sizeof(addrinfo_request_t) + 1] = {};
+        addrinfo_request_t *req = data;
+        asyncns_query_t *q;
+        assert(asyncns);
+        assert(node || service);
+
+        if (asyncns->dead) {
+                errno = ECHILD;
+                return NULL;
+        }
+
+        q = alloc_query(asyncns);
+        if (!q)
+                return NULL;
+
+        req->node_len = node ? strlen(node)+1 : 0;
+        req->service_len = service ? strlen(service)+1 : 0;
+
+        req->header.id = q->id;
+        req->header.type = q->type = REQUEST_ADDRINFO;
+        req->header.length = sizeof(addrinfo_request_t) + req->node_len + req->service_len;
+
+        if (req->header.length > BUFSIZE) {
+                errno = ENOMEM;
+                goto fail;
+        }
+
+        if (!(req->hints_is_null = !hints)) {
+                req->ai_flags = hints->ai_flags;
+                req->ai_family = hints->ai_family;
+                req->ai_socktype = hints->ai_socktype;
+                req->ai_protocol = hints->ai_protocol;
+        }
+
+        if (node)
+                strcpy((char*) req + sizeof(addrinfo_request_t), node);
+
+        if (service)
+                strcpy((char*) req + sizeof(addrinfo_request_t) + req->node_len, service);
+
+        if (send(asyncns->fds[REQUEST_SEND_FD], req, req->header.length, MSG_NOSIGNAL) < 0)
+                goto fail;
+
+        return q;
+
+fail:
+        if (q)
+                asyncns_cancel(asyncns, q);
+
+        return NULL;
+}
+
+int asyncns_getaddrinfo_done(asyncns_t *asyncns, asyncns_query_t* q, struct addrinfo **ret_res) {
+        int ret;
+        assert(asyncns);
+        assert(q);
+        assert(q->asyncns == asyncns);
+        assert(q->type == REQUEST_ADDRINFO);
+
+        if (asyncns->dead) {
+                errno = ECHILD;
+                return EAI_SYSTEM;
+        }
+
+        if (!q->done)
+                return EAI_AGAIN;
+
+        *ret_res = q->addrinfo;
+        q->addrinfo = NULL;
+
+        ret = q->ret;
+
+        if (ret == EAI_SYSTEM)
+                errno = q->_errno;
+
+        if (ret != 0)
+                h_errno = q->_h_errno;
+
+        asyncns_cancel(asyncns, q);
+
+        return ret;
+}
+
+asyncns_query_t* asyncns_getnameinfo(asyncns_t *asyncns, const struct sockaddr *sa, socklen_t salen, int flags, int gethost, int getserv) {
+        nameinfo_request_t data[BUFSIZE/sizeof(nameinfo_request_t) + 1] = {};
+        nameinfo_request_t *req = data;
+        asyncns_query_t *q;
+
+        assert(asyncns);
+        assert(sa);
+        assert(salen > 0);
+
+        if (asyncns->dead) {
+                errno = ECHILD;
+                return NULL;
+        }
+
+        q = alloc_query(asyncns);
+        if (!q)
+                return NULL;
+
+        req->header.id = q->id;
+        req->header.type = q->type = REQUEST_NAMEINFO;
+        req->header.length = sizeof(nameinfo_request_t) + salen;
+
+        if (req->header.length > BUFSIZE) {
+                errno = ENOMEM;
+                goto fail;
+        }
+
+        req->flags = flags;
+        req->sockaddr_len = salen;
+        req->gethost = gethost;
+        req->getserv = getserv;
+
+        memcpy((uint8_t*) req + sizeof(nameinfo_request_t), sa, salen);
+
+        if (send(asyncns->fds[REQUEST_SEND_FD], req, req->header.length, MSG_NOSIGNAL) < 0)
+                goto fail;
+
+        return q;
+
+fail:
+        if (q)
+                asyncns_cancel(asyncns, q);
+
+        return NULL;
+}
+
+int asyncns_getnameinfo_done(asyncns_t *asyncns, asyncns_query_t* q, char *ret_host, size_t hostlen, char *ret_serv, size_t servlen) {
+        int ret;
+        assert(asyncns);
+        assert(q);
+        assert(q->asyncns == asyncns);
+        assert(q->type == REQUEST_NAMEINFO);
+        assert(!ret_host || hostlen);
+        assert(!ret_serv || servlen);
+
+        if (asyncns->dead) {
+                errno = ECHILD;
+                return EAI_SYSTEM;
+        }
+
+        if (!q->done)
+                return EAI_AGAIN;
+
+        if (ret_host && q->host) {
+                strncpy(ret_host, q->host, hostlen);
+                ret_host[hostlen-1] = 0;
+        }
+
+        if (ret_serv && q->serv) {
+                strncpy(ret_serv, q->serv, servlen);
+                ret_serv[servlen-1] = 0;
+        }
+
+        ret = q->ret;
+
+        if (ret == EAI_SYSTEM)
+                errno = q->_errno;
+
+        if (ret != 0)
+                h_errno = q->_h_errno;
+
+        asyncns_cancel(asyncns, q);
+
+        return ret;
+}
+
+static asyncns_query_t * asyncns_res(asyncns_t *asyncns, query_type_t qtype, const char *dname, int class, int type) {
+        res_request_t data[BUFSIZE/sizeof(res_request_t) + 1];
+        res_request_t *req = data;
+        asyncns_query_t *q;
+
+        assert(asyncns);
+        assert(dname);
+
+        if (asyncns->dead) {
+                errno = ECHILD;
+                return NULL;
+        }
+
+        q = alloc_query(asyncns);
+        if (!q)
+                return NULL;
+
+        req->dname_len = strlen(dname) + 1;
+
+        req->header.id = q->id;
+        req->header.type = q->type = qtype;
+        req->header.length = sizeof(res_request_t) + req->dname_len;
+
+        if (req->header.length > BUFSIZE) {
+                errno = ENOMEM;
+                goto fail;
+        }
+
+        req->class = class;
+        req->type = type;
+
+        strcpy((char*) req + sizeof(res_request_t), dname);
+
+        if (send(asyncns->fds[REQUEST_SEND_FD], req, req->header.length, MSG_NOSIGNAL) < 0)
+                goto fail;
+
+        return q;
+
+fail:
+        if (q)
+                asyncns_cancel(asyncns, q);
+
+        return NULL;
+}
+
+asyncns_query_t* asyncns_res_query(asyncns_t *asyncns, const char *dname, int class, int type) {
+        return asyncns_res(asyncns, REQUEST_RES_QUERY, dname, class, type);
+}
+
+asyncns_query_t* asyncns_res_search(asyncns_t *asyncns, const char *dname, int class, int type) {
+        return asyncns_res(asyncns, REQUEST_RES_SEARCH, dname, class, type);
+}
+
+int asyncns_res_done(asyncns_t *asyncns, asyncns_query_t* q, unsigned char **answer) {
+        int ret;
+        assert(asyncns);
+        assert(q);
+        assert(q->asyncns == asyncns);
+        assert(q->type == REQUEST_RES_QUERY || q->type == REQUEST_RES_SEARCH);
+        assert(answer);
+
+        if (asyncns->dead) {
+                errno = ECHILD;
+                return -ECHILD;
+        }
+
+        if (!q->done) {
+                errno = EAGAIN;
+                return -EAGAIN;
+        }
+
+        *answer = (unsigned char *)q->serv;
+        q->serv = NULL;
+
+        ret = q->ret;
+
+        if (ret < 0) {
+                errno = q->_errno;
+                h_errno = q->_h_errno;
+        }
+
+        asyncns_cancel(asyncns, q);
+
+        return ret < 0 ? -errno : ret;
+}
+
+asyncns_query_t* asyncns_getnext(asyncns_t *asyncns) {
+        assert(asyncns);
+        return asyncns->done_head;
+}
+
+int asyncns_getnqueries(asyncns_t *asyncns) {
+        assert(asyncns);
+        return asyncns->n_queries;
+}
+
+void asyncns_cancel(asyncns_t *asyncns, asyncns_query_t* q) {
+        int i;
+        int saved_errno = errno;
+
+        assert(asyncns);
+        assert(q);
+        assert(q->asyncns == asyncns);
+        assert(asyncns->n_queries > 0);
+
+        if (q->done) {
+
+                if (q->done_prev)
+                        q->done_prev->done_next = q->done_next;
+                else
+                        asyncns->done_head = q->done_next;
+
+                if (q->done_next)
+                        q->done_next->done_prev = q->done_prev;
+                else
+                        asyncns->done_tail = q->done_prev;
+        }
+
+        i = q->id % MAX_QUERIES;
+        assert(asyncns->queries[i] == q);
+        asyncns->queries[i] = NULL;
+
+        asyncns_freeaddrinfo(q->addrinfo);
+        free(q->host);
+        free(q->serv);
+
+        asyncns->n_queries--;
+        free(q);
+
+        errno = saved_errno;
+}
+
+void asyncns_freeaddrinfo(struct addrinfo *ai) {
+        int saved_errno = errno;
+
+        while (ai) {
+                struct addrinfo *next = ai->ai_next;
+
+                free(ai->ai_addr);
+                free(ai->ai_canonname);
+                free(ai);
+
+                ai = next;
+        }
+
+        errno = saved_errno;
+}
+
+void asyncns_freeanswer(unsigned char *answer) {
+        int saved_errno = errno;
+
+        if (!answer)
+                return;
+
+        /* Please note that this function is new in libasyncns 0.4. In
+         * older versions you were supposed to free the answer directly
+         * with free(). Hence, if this function is changed to do more than
+         * just a simple free() this must be considered ABI/API breakage! */
+
+        free(answer);
+
+        errno = saved_errno;
+}
+
+int asyncns_isdone(asyncns_t *asyncns, asyncns_query_t*q) {
+        assert(asyncns);
+        assert(q);
+        assert(q->asyncns == asyncns);
+
+        return q->done;
+}
+
+void asyncns_setuserdata(asyncns_t *asyncns, asyncns_query_t *q, void *userdata) {
+        assert(q);
+        assert(asyncns);
+        assert(q->asyncns = asyncns);
+
+        q->userdata = userdata;
+}
+
+void* asyncns_getuserdata(asyncns_t *asyncns, asyncns_query_t *q) {
+        assert(q);
+        assert(asyncns);
+        assert(q->asyncns = asyncns);
+
+        return q->userdata;
+}