s4-resolver: make it work back with ipv4 only DNS records

[Samba/gebeck_regimport.git] / source4 / libcli / resolve / dns_ex.c

/*
   Unix SMB/CIFS implementation.

   async getaddrinfo()/dns_lookup() name resolution module

   Copyright (C) Andrew Tridgell 2005
   Copyright (C) Stefan Metzmacher 2008
   Copyright (C) Matthieu Patou 2011

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/*
  this module uses a fork() per getaddrinfo() or dns_looup() call.
  At first that might seem crazy, but it is actually very fast,
  and solves many of the tricky problems of keeping a child
  hanging around in a librar (like what happens when the parent forks).
  We use a talloc destructor to ensure that the child is cleaned up
  when we have finished with this name resolution.
*/

#include "includes.h"
#include "lib/events/events.h"
#include "system/network.h"
#include "system/filesys.h"
#include "lib/socket/socket.h"
#include "libcli/composite/composite.h"
#include "librpc/gen_ndr/ndr_nbt.h"
#include "libcli/resolve/resolve.h"
#include "lib/util/util_net.h"

#ifdef class
#undef class
#endif

#include "heimdal/lib/roken/resolve.h"

struct dns_ex_state {
        bool do_fallback;
        uint32_t flags;
        uint16_t port;
        struct nbt_name name;
        struct socket_address **addrs;
        char **names;
        pid_t child;
        int child_fd;
        struct tevent_fd *fde;
        struct tevent_context *event_ctx;
};

/*
  kill off a wayward child if needed. This allows us to stop an async
  name resolution without leaving a potentially blocking call running
  in a child
*/
static int dns_ex_destructor(struct dns_ex_state *state)
{
        int status;

        kill(state->child, SIGTERM);
        if (waitpid(state->child, &status, WNOHANG) == 0) {
                kill(state->child, SIGKILL);
                waitpid(state->child, &status, 0);
        }

        return 0;
}

static uint32_t count_dns_rr(struct rk_resource_record *head, unsigned record_type)
{
        uint32_t count = 0;
        struct rk_resource_record *rr;

        for (rr=head; rr; rr=rr->next) {

                /* we are only interested in the IN class */
                if (rr->class != rk_ns_c_in) {
                        continue;
                }

                /* we are only interested by requested record */
                if (rr->type != record_type) {
                        continue;
                }

                switch(record_type) {
                        case rk_ns_t_srv:

                                /* verify we actually have a SRV record here */
                                if (!rr->u.srv) {
                                        continue;
                                }

                                /* Verify we got a port */
                                if (rr->u.srv->port == 0) {
                                        continue;
                                }
                                count++;
                                break;
                        case rk_ns_t_a:
                        case rk_ns_t_aaaa:
                                /* verify we actually have a record here */
                                if (!rr->u.data) {
                                        continue;
                                }
                                count++;
                                break;
                        default:
                                count++;
                                break;
                }
        }

        return count;
}

struct dns_records_container {
        char **list;
        uint32_t count;
};

static char* rr_to_string(TALLOC_CTX *mem_ctx,
                                        struct rk_resource_record *rr,
                                        uint16_t port)
{
        char addrstr[INET6_ADDRSTRLEN];
        char *addr;

        switch (rr->type) {
                case rk_ns_t_a:
                        if (inet_ntop(AF_INET, rr->u.a,
                                      addrstr, sizeof(addrstr)) == NULL) {
                                return NULL;
                        }
                        break;
#ifdef HAVE_IPV6
                case rk_ns_t_aaaa:
                        if (inet_ntop(AF_INET6, (struct in6_addr *)rr->u.data,
                                      addrstr, sizeof(addrstr)) == NULL) {
                                return NULL;
                        }
                        break;
#endif
                default:
                        return NULL;
        }

        addr = talloc_asprintf(mem_ctx, "%s@%u/%s", addrstr,
                                         port, rr->domain);

        return addr;
}

static struct dns_records_container get_a_aaaa_records(TALLOC_CTX *mem_ctx,
                                                        const char* name,
                                                        int port)
{
        struct rk_dns_reply *reply, *reply2, *rep, *tmp[3];
        struct rk_resource_record *rr;
        struct dns_records_container ret;
        char **addrs = NULL;
        uint32_t count, count2, total;
        uint32_t i;

        memset(&ret, 0, sizeof(struct dns_records_container));
        /* this is the blocking call we are going to lots of trouble
           to avoid them in the parent */
        reply = rk_dns_lookup(name, "AAAA");

        count = count2 = 0;

        if (reply) {

                count = count_dns_rr(reply->head, rk_ns_t_aaaa);
                count2 = count_dns_rr(reply->head, rk_ns_t_a);

                if (!count2) {
                        /*
                        * DNS server didn't returned A when asked for AAAA records.
                        * Most of the server do it, let's ask for A specificaly.
                        */
                        reply2 = rk_dns_lookup(name, "A");

                        if (!reply2) {
                                return ret;
                        }

                        count2 = count_dns_rr(reply2->head, rk_ns_t_a);
                } else {
                        reply2 = NULL;
                }
        } else {

                reply = rk_dns_lookup(name, "A");
                if (!reply) {
                        return ret;
                }

                reply2 = NULL;
                count = count_dns_rr(reply->head, rk_ns_t_a);
        }
        count += count2;

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

        addrs = talloc_zero_array(mem_ctx, char*, count);
        total = 0;

        tmp[0] = reply;
        tmp[1] = reply2;
        tmp[2] = NULL;

        /* Loop over all returned records and pick the records */
        for (i=0; tmp[i] != NULL; i++) {
                rep = tmp[i];
                for (rr=rep->head; rr; rr=rr->next) {
                        /* we are only interested in the IN class */
                        if (rr->class != rk_ns_c_in) {
                                continue;
                        }

                        /* we are only interested in A and AAAA records */
                        if (rr->type != rk_ns_t_a && rr->type != rk_ns_t_aaaa) {
                                continue;
                        }

                        /* verify we actually have a record here */
                        if (!rr->u.data) {
                                continue;
                        }
                        rr_to_string(mem_ctx, rr, port);
                        addrs[total] = rr_to_string(mem_ctx, rr, port);
                        if (addrs[total]) {
                                total++;
                        }
                }
        }
        if (total) {
                ret.count = total;
                ret.list = addrs;
        }

done:
        if (reply != NULL)
                rk_dns_free_data(reply);

        if (reply2 != NULL)
                rk_dns_free_data(reply2);

        return ret;
}

static struct dns_records_container get_srv_records(TALLOC_CTX *mem_ctx,
                                                        const char* name)
{
        struct rk_dns_reply *reply;
        struct rk_resource_record *rr;
        struct dns_records_container ret;
        char **addrs = NULL;
        uint32_t count, total;

        memset(&ret, 0, sizeof(struct dns_records_container));
        /* this is the blocking call we are going to lots of trouble
           to avoid them in the parent */
        reply = rk_dns_lookup(name, "SRV");

        if (!reply) {
                return ret;
        }

        rk_dns_srv_order(reply);
        count = count_dns_rr(reply->head, rk_ns_t_srv);

        total = 0;
        if (count == 0) {
                goto done;
        }

        /* Loop over all returned records and pick the records */
        for (rr=reply->head; rr; rr=rr->next) {
                struct dns_records_container c;
                char* tmp_str;
                /* we are only interested in the IN class */
                if (rr->class != rk_ns_c_in) {
                        continue;
                }

                /* we are only interested in SRV records */
                if (rr->type != rk_ns_t_srv) {
                        continue;
                }

                /* verify we actually have a srv record here */
                if (!rr->u.srv) {
                        continue;
                }

                /* Verify we got a port */
                if (rr->u.srv->port == 0) {
                        continue;
                }

                tmp_str = rr->u.srv->target;
                if (strchr(tmp_str, '.') && tmp_str[strlen(tmp_str)-1] != '.') {
                        /* we are asking for a fully qualified name, but the
                        name doesn't end in a '.'. We need to prevent the
                        DNS library trying the search domains configured in
                        resolv.conf */
                        tmp_str = talloc_asprintf(mem_ctx, "%s.", tmp_str);
                }

                c = get_a_aaaa_records(mem_ctx, tmp_str, rr->u.srv->port);
                total += c.count;
                if (addrs == NULL) {
                        addrs = c.list;
                } else {
                        unsigned j;

                        addrs = talloc_realloc(mem_ctx, addrs, char*, total);
                        for (j=0; j < c.count; j++) {
                                addrs[total - j - 1] = talloc_steal(addrs, c.list[j]);
                        }
                }
        }

        if (total) {
                ret.count = total;
                ret.list = addrs;
        }


done:
        if (reply != NULL)
                rk_dns_free_data(reply);

        return ret;
}
/*
  the blocking child
*/
static void run_child_dns_lookup(struct dns_ex_state *state, int fd)
{
        bool first;
        bool do_srv = (state->flags & RESOLVE_NAME_FLAG_DNS_SRV);
        struct dns_records_container c;
        char* addrs = NULL;
        unsigned int i;

        if (strchr(state->name.name, '.') && state->name.name[strlen(state->name.name)-1] != '.') {
                /* we are asking for a fully qualified name, but the
                   name doesn't end in a '.'. We need to prevent the
                   DNS library trying the search domains configured in
                   resolv.conf */
                state->name.name = talloc_strdup_append(discard_const_p(char, state->name.name),
                                                        ".");
        }


        if (do_srv) {
                c = get_srv_records(state, state->name.name);
        } else {
                c = get_a_aaaa_records(state, state->name.name, state->port);
        }

        addrs = talloc_strdup(state, "");
        if (!addrs) {
                goto done;
        }
        first = true;

        for (i=0; i < c.count; i++) {
                addrs = talloc_asprintf_append_buffer(addrs, "%s%s",
                                                        first?"":",",
                                                        c.list[i]);
                first = false;
        }

        if (addrs) {
                DEBUG(11, ("Addrs = %s\n", addrs));
                write(fd, addrs, talloc_get_size(addrs));
        }

done:
        close(fd);
}

/*
  the blocking child
*/
static void run_child_getaddrinfo(struct dns_ex_state *state, int fd)
{
        int ret;
        struct addrinfo hints;
        struct addrinfo *res;
        struct addrinfo *res_list = NULL;
        char *addrs;
        bool first;

        ZERO_STRUCT(hints);
        hints.ai_socktype = SOCK_STREAM;
        hints.ai_flags = AI_ADDRCONFIG | AI_NUMERICSERV;

        ret = getaddrinfo(state->name.name, "0", &hints, &res_list);
        /* try to fallback in case of error */
        if (state->do_fallback) {
                switch (ret) {
#ifdef EAI_NODATA
                case EAI_NODATA:
#endif
                case EAI_NONAME:
                        /* getaddrinfo() doesn't handle CNAME records */
                        run_child_dns_lookup(state, fd);
                        return;
                default:
                        break;
                }
        }
        if (ret != 0) {
                goto done;
        }

        addrs = talloc_strdup(state, "");
        if (!addrs) {
                goto done;
        }
        first = true;
        for (res = res_list; res; res = res->ai_next) {
                char addrstr[INET6_ADDRSTRLEN];
                if (!print_sockaddr_len(addrstr, sizeof(addrstr), (struct sockaddr *)res->ai_addr, res->ai_addrlen)) {
                        continue;
                }
                addrs = talloc_asprintf_append_buffer(addrs, "%s%s@%u/%s",
                                                      first?"":",",
                                                      addrstr,
                                                      state->port,
                                                      state->name.name);
                if (!addrs) {
                        goto done;
                }
                first = false;
        }

        if (addrs) {
                write(fd, addrs, talloc_get_size(addrs));
        }
done:
        if (res_list) {
                freeaddrinfo(res_list);
        }
        close(fd);
}

/*
  handle a read event on the pipe
*/
static void pipe_handler(struct tevent_context *ev, struct tevent_fd *fde, 
                         uint16_t flags, void *private_data)
{
        struct composite_context *c = talloc_get_type(private_data, struct composite_context);
        struct dns_ex_state *state = talloc_get_type(c->private_data,
                                     struct dns_ex_state);
        char *address;
        uint32_t num_addrs, i;
        char **addrs;
        int ret;
        int status;
        int value = 0;

        /* if we get any event from the child then we know that we
           won't need to kill it off */
        talloc_set_destructor(state, NULL);

        if (ioctl(state->child_fd, FIONREAD, &value) != 0) {
                value = 8192;
        }

        address = talloc_array(state, char, value+1);
        if (address) {
                /* yes, we don't care about EAGAIN or other niceities
                   here. They just can't happen with this parent/child
                   relationship, and even if they did then giving an error is
                   the right thing to do */
                ret = read(state->child_fd, address, value);
        } else {
                ret = -1;
        }
        if (waitpid(state->child, &status, WNOHANG) == 0) {
                kill(state->child, SIGKILL);
                waitpid(state->child, &status, 0);
        }

        if (ret <= 0) {
                DEBUG(3,("dns child failed to find name '%s' of type %s\n",
                         state->name.name, (state->flags & RESOLVE_NAME_FLAG_DNS_SRV)?"SRV":"A"));
                composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
                return;
        }

        /* enusre the address looks good */
        address[ret] = 0;

        addrs = str_list_make(state, address, ",");
        if (composite_nomem(addrs, c)) return;

        num_addrs = str_list_length((const char * const *)addrs);

        state->addrs = talloc_array(state, struct socket_address *,
                                    num_addrs+1);
        if (composite_nomem(state->addrs, c)) return;

        state->names = talloc_array(state, char *, num_addrs+1);
        if (composite_nomem(state->names, c)) return;

        for (i=0; i < num_addrs; i++) {
                uint32_t port = 0;
                char *p = strrchr(addrs[i], '@');
                char *n;

                if (!p) {
                        composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
                        return;
                }

                *p = '\0';
                p++;

                n = strrchr(p, '/');
                if (!n) {
                        composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
                        return;
                }

                *n = '\0';
                n++;

                if (strcmp(addrs[i], "0.0.0.0") == 0) {
                        composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
                        return;
                }
                port = strtoul(p, NULL, 10);
                if (port > UINT16_MAX) {
                        composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
                        return;
                }
                state->addrs[i] = socket_address_from_strings(state->addrs,
                                                              "ip",
                                                              addrs[i],
                                                              port);
                if (composite_nomem(state->addrs[i], c)) return;

                state->names[i] = talloc_strdup(state->names, n);
                if (composite_nomem(state->names[i], c)) return;
        }
        state->addrs[i] = NULL;
        state->names[i] = NULL;

        composite_done(c);
}

/*
  getaddrinfo() or dns_lookup() name resolution method - async send
 */
struct composite_context *resolve_name_dns_ex_send(TALLOC_CTX *mem_ctx,
                                                   struct tevent_context *event_ctx,
                                                   void *privdata,
                                                   uint32_t flags,
                                                   uint16_t port,
                                                   struct nbt_name *name,
                                                   bool do_fallback)
{
        struct composite_context *c;
        struct dns_ex_state *state;
        int fd[2] = { -1, -1 };
        int ret;

        c = composite_create(mem_ctx, event_ctx);
        if (c == NULL) return NULL;

        if (flags & RESOLVE_NAME_FLAG_FORCE_NBT) {
                composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
                return c;
        }

        state = talloc_zero(c, struct dns_ex_state);
        if (composite_nomem(state, c)) return c;
        c->private_data = state;

        c->status = nbt_name_dup(state, name, &state->name);
        if (!composite_is_ok(c)) return c;

        /* setup a pipe to chat to our child */
        ret = pipe(fd);
        if (ret == -1) {
                composite_error(c, map_nt_error_from_unix_common(errno));
                return c;
        }

        state->do_fallback = do_fallback;
        state->flags = flags;
        state->port = port;

        state->child_fd = fd[0];
        state->event_ctx = c->event_ctx;

        /* we need to put the child in our event context so
           we know when the dns_lookup() has finished */
        state->fde = tevent_add_fd(c->event_ctx, c, state->child_fd, TEVENT_FD_READ,
                                  pipe_handler, c);
        if (composite_nomem(state->fde, c)) {
                close(fd[0]);
                close(fd[1]);
                return c;
        }
        tevent_fd_set_auto_close(state->fde);

        state->child = fork();
        if (state->child == (pid_t)-1) {
                composite_error(c, map_nt_error_from_unix_common(errno));
                return c;
        }

        if (state->child == 0) {
                close(fd[0]);
                if (state->flags & RESOLVE_NAME_FLAG_FORCE_DNS) {
                        run_child_dns_lookup(state, fd[1]);
                } else {
                        run_child_getaddrinfo(state, fd[1]);
                }
                _exit(0);
        }
        close(fd[1]);

        /* cleanup wayward children */
        talloc_set_destructor(state, dns_ex_destructor);

        return c;
}

/*
  getaddrinfo() or dns_lookup() name resolution method - recv side
*/
NTSTATUS resolve_name_dns_ex_recv(struct composite_context *c, 
                                  TALLOC_CTX *mem_ctx,
                                  struct socket_address ***addrs,
                                  char ***names)
{
        NTSTATUS status;

        status = composite_wait(c);

        if (NT_STATUS_IS_OK(status)) {
                struct dns_ex_state *state = talloc_get_type(c->private_data,
                                             struct dns_ex_state);
                *addrs = talloc_steal(mem_ctx, state->addrs);
                if (names) {
                        *names = talloc_steal(mem_ctx, state->names);
                }
        }

        talloc_free(c);
        return status;
}