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"
41 const char *reply_addr;
45 struct event_context *event_ctx;
50 kill off a wayward child if needed. This allows us to stop an async
51 name resolution without leaving a potentially blocking call running
54 static int host_destructor(void *ptr)
56 struct host_state *state = talloc_get_type(ptr, struct host_state);
57 close(state->child_fd);
58 if (state->child != (pid_t)-1) {
59 kill(state->child, SIGTERM);
67 static void run_child(struct composite_context *c, int fd)
69 struct host_state *state = talloc_get_type(c->private, struct host_state);
73 /* this is the blocking call we are going to lots of trouble
74 to avoid in the parent */
75 ip = interpret_addr2(state->name.name);
77 address = sys_inet_ntoa(ip);
78 if (address != NULL) {
79 write(fd, address, strlen(address)+1);
84 handle a read event on the pipe
86 static void pipe_handler(struct event_context *ev, struct fd_event *fde,
87 uint16_t flags, void *private)
89 struct composite_context *c = talloc_get_type(private, struct composite_context);
90 struct host_state *state = talloc_get_type(c->private, struct host_state);
94 /* if we get any event from the child then we know that we
95 won't need to kill it off */
96 state->child = (pid_t)-1;
98 /* yes, we don't care about EAGAIN or other niceities
99 here. They just can't happen with this parent/child
100 relationship, and even if they did then giving an error is
101 the right thing to do */
102 ret = read(state->child_fd, address, sizeof(address)-1);
103 if (ret <= 0) goto failed;
105 /* enusre the address looks good */
107 if (strcmp(address, "0.0.0.0") == 0 ||
108 inet_addr(address) == INADDR_NONE) {
112 state->reply_addr = talloc_strdup(state, address);
113 if (state->reply_addr == NULL) goto failed;
115 c->status = NT_STATUS_OK;
116 c->state = SMBCLI_REQUEST_DONE;
123 c->status = NT_STATUS_BAD_NETWORK_NAME;
124 c->state = SMBCLI_REQUEST_ERROR;
131 gethostbyname name resolution method - async send
133 struct composite_context *resolve_name_host_send(struct nbt_name *name,
134 struct event_context *event_ctx)
136 struct composite_context *c;
137 struct host_state *state;
139 int fd[2] = { -1, -1 };
142 c = talloc_zero(NULL, struct composite_context);
143 if (c == NULL) goto failed;
145 state = talloc(c, struct host_state);
146 if (state == NULL) goto failed;
148 status = nbt_name_dup(state, name, &state->name);
149 if (!NT_STATUS_IS_OK(status)) goto failed;
151 c->state = SMBCLI_REQUEST_SEND;
153 c->event_ctx = talloc_reference(c, event_ctx);
155 /* setup a pipe to chat to our child */
157 if (ret == -1) goto failed;
159 state->child_fd = fd[0];
160 state->event_ctx = c->event_ctx;
162 /* we need to put the child in our event context so
163 we know when the gethostbyname() has finished */
164 state->fde = event_add_fd(c->event_ctx, c, state->child_fd, EVENT_FD_READ,
166 if (state->fde == NULL) {
172 /* signal handling in posix really sucks - doing this in a library
173 affects the whole app, but what else to do?? */
174 signal(SIGCHLD, SIG_IGN);
176 state->child = fork();
177 if (state->child == (pid_t)-1) {
181 if (state->child == 0) {
188 /* cleanup wayward children */
189 talloc_set_destructor(state, host_destructor);
199 gethostbyname name resolution method - recv side
201 NTSTATUS resolve_name_host_recv(struct composite_context *c,
202 TALLOC_CTX *mem_ctx, const char **reply_addr)
206 status = composite_wait(c);
208 if (NT_STATUS_IS_OK(status)) {
209 struct host_state *state = talloc_get_type(c->private, struct host_state);
210 *reply_addr = talloc_steal(mem_ctx, state->reply_addr);
218 gethostbyname name resolution method - sync call
220 NTSTATUS resolve_name_host(struct nbt_name *name,
222 const char **reply_addr)
224 struct composite_context *c = resolve_name_host_send(name, NULL);
225 return resolve_name_host_recv(c, mem_ctx, reply_addr);