--- /dev/null
+/*
+ Unix SMB/CIFS implementation.
+
+ async getaddrinfo()/dns_lookup() name resolution module
+
+ Copyright (C) Andrew Tridgell 2005
+ Copyright (C) Stefan Metzmacher 2008
+
+ 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 "heimdal/lib/roken/resolve.h"
+
+struct dns_ex_state {
+ bool do_getaddrinfo;
+ bool do_fallback;
+ bool do_srv;
+ struct nbt_name name;
+ struct socket_address **addrs;
+ pid_t child;
+ int child_fd;
+ struct fd_event *fde;
+ struct event_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);
+ close(state->child_fd);
+ if (waitpid(state->child, &status, WNOHANG) == 0) {
+ kill(state->child, SIGKILL);
+ waitpid(state->child, &status, 0);
+ }
+
+ return 0;
+}
+
+/*
+ the blocking child
+*/
+static void run_child_dns_lookup(struct dns_ex_state *state, int fd)
+{
+ struct dns_reply *reply;
+ struct resource_record *rr;
+ uint32_t count = 0;
+ uint32_t srv_valid = 0;
+ struct resource_record **srv_rr;
+ uint32_t addrs_valid = 0;
+ struct resource_record **addrs_rr;
+ char *addrs;
+ bool first;
+ uint32_t i;
+
+ /* this is the blocking call we are going to lots of trouble
+ to avoid in the parent */
+ reply = dns_lookup(state->name.name, state->do_srv?"SRV":"A");
+ if (!reply) {
+ goto done;
+ }
+
+ if (state->do_srv) {
+ dns_srv_order(reply);
+ }
+
+ /* Loop over all returned records and pick the "srv" records */
+ for (rr=reply->head; rr; rr=rr->next) {
+ /* we are only interested in the IN class */
+ if (rr->class != C_IN) {
+ continue;
+ }
+
+ if (state->do_srv) {
+ /* we are only interested in SRV records */
+ if (rr->type != 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;
+ }
+ } else {
+ /* we are only interested in A records */
+ /* TODO: add AAAA support */
+ if (rr->type != T_A) {
+ continue;
+ }
+
+ /* verify we actually have a A record here */
+ if (!rr->u.a) {
+ continue;
+ }
+ }
+ count++;
+ }
+
+ if (count == 0) {
+ goto done;
+ }
+
+ srv_rr = talloc_zero_array(state,
+ struct resource_record *,
+ count);
+ if (!srv_rr) {
+ goto done;
+ }
+
+ addrs_rr = talloc_zero_array(state,
+ struct resource_record *,
+ count);
+ if (!addrs_rr) {
+ goto done;
+ }
+
+ /* Loop over all returned records and pick the records */
+ for (rr=reply->head;rr;rr=rr->next) {
+ /* we are only interested in the IN class */
+ if (rr->class != C_IN) {
+ continue;
+ }
+
+ if (state->do_srv) {
+ /* we are only interested in SRV records */
+ if (rr->type != 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;
+ }
+
+ srv_rr[srv_valid] = rr;
+ srv_valid++;
+ } else {
+ /* we are only interested in A records */
+ /* TODO: add AAAA support */
+ if (rr->type != T_A) {
+ continue;
+ }
+
+ /* verify we actually have a A record here */
+ if (!rr->u.a) {
+ continue;
+ }
+
+ addrs_rr[addrs_valid] = rr;
+ addrs_valid++;
+ }
+ }
+
+ for (i=0; i < srv_valid; i++) {
+ for (rr=reply->head;rr;rr=rr->next) {
+
+ if (rr->class != C_IN) {
+ continue;
+ }
+
+ /* we are only interested in SRV records */
+ if (rr->type != T_A) {
+ continue;
+ }
+
+ /* verify we actually have a srv record here */
+ if (strcmp(&srv_rr[i]->u.srv->target[0], rr->domain) != 0) {
+ continue;
+ }
+
+ addrs_rr[i] = rr;
+ addrs_valid++;
+ break;
+ }
+ }
+
+ if (addrs_valid == 0) {
+ goto done;
+ }
+
+ addrs = talloc_strdup(state, "");
+ if (!addrs) {
+ goto done;
+ }
+ first = true;
+ for (i=0; i < count; i++) {
+ if (!addrs_rr[i]) {
+ continue;
+ }
+ addrs = talloc_asprintf_append_buffer(addrs, "%s%s:%u",
+ first?"":",",
+ inet_ntoa(*addrs_rr[i]->u.a),
+ srv_rr[i]?srv_rr[i]->u.srv->port:0);
+ if (!addrs) {
+ goto done;
+ }
+ first = false;
+ }
+
+ if (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_family = AF_INET;/* TODO: add AF_INET6 support */
+ hints.ai_flags = AI_ADDRCONFIG | AI_NUMERICSERV;
+
+ ret = getaddrinfo(state->name.name, "0", &hints, &res_list);
+ if (ret == EAI_NODATA && state->do_fallback) {
+ /* getaddrinfo() doesn't handle CNAME records */
+ run_child_dns_lookup(state, fd);
+ return;
+ }
+ if (ret != 0) {
+ goto done;
+ }
+
+ addrs = talloc_strdup(state, "");
+ if (!addrs) {
+ goto done;
+ }
+ first = true;
+ for (res = res_list; res; res = res->ai_next) {
+ struct sockaddr_in *in;
+
+ if (res->ai_family != AF_INET) {
+ continue;
+ }
+ in = (struct sockaddr_in *)res->ai_addr;
+
+ addrs = talloc_asprintf_append_buffer(addrs, "%s%s:%u",
+ first?"":",",
+ inet_ntoa(in->sin_addr),
+ 0);
+ 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 event_context *ev, struct fd_event *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[2048];
+ uint32_t num_addrs, i;
+ char **addrs;
+ int ret;
+ int status;
+
+ /* 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);
+
+ /* 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, sizeof(address)-1);
+ close(state->child_fd);
+ if (waitpid(state->child, &status, WNOHANG) == 0) {
+ kill(state->child, SIGKILL);
+ waitpid(state->child, &status, 0);
+ }
+
+ if (ret <= 0) {
+ 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;
+
+ for (i=0; i < num_addrs; i++) {
+ uint32_t port = 0;
+ char *p = strrchr(addrs[i], ':');
+
+ if (!p) {
+ composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
+ return;
+ }
+
+ *p = '\0';
+ p++;
+
+ if (strcmp(addrs[i], "0.0.0.0") == 0 ||
+ inet_addr(addrs[i]) == INADDR_NONE) {
+ composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
+ return;
+ }
+ port = strtoul(p, NULL, 10);
+ if (port > UINT16_MAX) {
+ port = 0;
+ }
+ state->addrs[i] = socket_address_from_strings(state->addrs,
+ "ipv4",
+ addrs[i],
+ port);
+ if (composite_nomem(state->addrs[i], c)) return;
+ }
+ state->addrs[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 event_context *event_ctx,
+ void *privdata,
+ struct nbt_name *name,
+ bool do_getaddrinfo,
+ bool do_fallback,
+ bool do_srv)
+{
+ 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 (composite_nomem(c->event_ctx, c)) 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(errno));
+ return c;
+ }
+
+ state->do_getaddrinfo = do_getaddrinfo;
+ state->do_fallback = do_fallback;
+ state->do_srv = do_srv;
+
+ 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 = event_add_fd(c->event_ctx, c, state->child_fd, EVENT_FD_READ,
+ pipe_handler, c);
+ if (composite_nomem(state->fde, c)) {
+ close(fd[0]);
+ close(fd[1]);
+ return c;
+ }
+
+ state->child = fork();
+ if (state->child == (pid_t)-1) {
+ composite_error(c, map_nt_error_from_unix(errno));
+ return c;
+ }
+
+ if (state->child == 0) {
+ close(fd[0]);
+ if (state->do_getaddrinfo) {
+ run_child_getaddrinfo(state, fd[1]);
+ } else {
+ run_child_dns_lookup(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)
+{
+ 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);
+ }
+
+ talloc_free(c);
+ return status;
+}
git.samba.org / amitay / samba.git / commitdiff