2 Unix SMB/CIFS implementation.
4 async gethostbyname() name resolution module
6 Copyright (C) Andrew Tridgell 2005
8 This program is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 2 of the License, or
11 (at your option) any later version.
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with this program; if not, write to the Free Software
20 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24 this module uses a fork() per gethostbyname() call. At first that
25 might seem crazy, but it is actually very fast, and solves many of
26 the tricky problems of keeping a child hanging around in a library
27 (like what happens when the parent forks). We use a talloc
28 destructor to ensure that the child is cleaned up when we have
29 finished with this name resolution.
33 #include "lib/events/events.h"
34 #include "system/network.h"
35 #include "system/filesys.h"
36 #include "libcli/raw/libcliraw.h"
37 #include "libcli/composite/composite.h"
38 #include "libcli/nbt/libnbt.h"
42 const char *reply_addr;
46 struct event_context *event_ctx;
51 kill off a wayward child if needed. This allows us to stop an async
52 name resolution without leaving a potentially blocking call running
55 static int host_destructor(void *ptr)
57 struct host_state *state = talloc_get_type(ptr, struct host_state);
58 close(state->child_fd);
59 if (state->child != (pid_t)-1) {
60 kill(state->child, SIGTERM);
68 static void run_child(struct composite_context *c, int fd)
70 struct host_state *state = talloc_get_type(c->private_data, struct host_state);
74 /* this is the blocking call we are going to lots of trouble
75 to avoid in the parent */
76 ip = interpret_addr2(state->name.name);
78 address = sys_inet_ntoa(ip);
79 if (address != NULL) {
80 write(fd, address, strlen(address)+1);
85 handle a read event on the pipe
87 static void pipe_handler(struct event_context *ev, struct fd_event *fde,
88 uint16_t flags, void *private_data)
90 struct composite_context *c = talloc_get_type(private_data, struct composite_context);
91 struct host_state *state = talloc_get_type(c->private_data, struct host_state);
95 /* if we get any event from the child then we know that we
96 won't need to kill it off */
97 state->child = (pid_t)-1;
99 /* yes, we don't care about EAGAIN or other niceities
100 here. They just can't happen with this parent/child
101 relationship, and even if they did then giving an error is
102 the right thing to do */
103 ret = read(state->child_fd, address, sizeof(address)-1);
104 if (ret <= 0) goto failed;
106 /* enusre the address looks good */
108 if (strcmp(address, "0.0.0.0") == 0 ||
109 inet_addr(address) == INADDR_NONE) {
113 state->reply_addr = talloc_strdup(state, address);
114 if (state->reply_addr == NULL) goto failed;
116 c->status = NT_STATUS_OK;
117 c->state = COMPOSITE_STATE_DONE;
124 c->status = NT_STATUS_BAD_NETWORK_NAME;
125 c->state = COMPOSITE_STATE_ERROR;
132 gethostbyname name resolution method - async send
134 struct composite_context *resolve_name_host_send(struct nbt_name *name,
135 struct event_context *event_ctx)
137 struct composite_context *c;
138 struct host_state *state;
140 int fd[2] = { -1, -1 };
143 c = talloc_zero(NULL, struct composite_context);
144 if (c == NULL) goto failed;
146 state = talloc(c, struct host_state);
147 if (state == NULL) goto failed;
149 status = nbt_name_dup(state, name, &state->name);
150 if (!NT_STATUS_IS_OK(status)) goto failed;
152 c->state = COMPOSITE_STATE_IN_PROGRESS;
153 c->private_data = state;
154 c->event_ctx = talloc_reference(c, event_ctx);
156 /* setup a pipe to chat to our child */
158 if (ret == -1) goto failed;
160 state->child_fd = fd[0];
161 state->event_ctx = c->event_ctx;
163 /* we need to put the child in our event context so
164 we know when the gethostbyname() has finished */
165 state->fde = event_add_fd(c->event_ctx, c, state->child_fd, EVENT_FD_READ,
167 if (state->fde == NULL) {
173 /* signal handling in posix really sucks - doing this in a library
174 affects the whole app, but what else to do?? */
175 signal(SIGCHLD, SIG_IGN);
177 state->child = fork();
178 if (state->child == (pid_t)-1) {
182 if (state->child == 0) {
189 /* cleanup wayward children */
190 talloc_set_destructor(state, host_destructor);
200 gethostbyname name resolution method - recv side
202 NTSTATUS resolve_name_host_recv(struct composite_context *c,
203 TALLOC_CTX *mem_ctx, const char **reply_addr)
207 status = composite_wait(c);
209 if (NT_STATUS_IS_OK(status)) {
210 struct host_state *state = talloc_get_type(c->private_data, struct host_state);
211 *reply_addr = talloc_steal(mem_ctx, state->reply_addr);
219 gethostbyname name resolution method - sync call
221 NTSTATUS resolve_name_host(struct nbt_name *name,
223 const char **reply_addr)
225 struct composite_context *c = resolve_name_host_send(name, NULL);
226 return resolve_name_host_recv(c, mem_ctx, reply_addr);