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/*
Unix SMB/CIFS implementation.
async gethostbyname() name resolution module
Copyright (C) Andrew Tridgell 2005
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 gethostbyname() 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 library
(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 "libcli/composite/composite.h"
#include "librpc/gen_ndr/ndr_nbt.h"
#include "libcli/resolve/resolve.h"
struct host_state {
struct nbt_name name;
const char *reply_addr;
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 host_destructor(struct host_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(struct composite_context *c, int fd)
{
struct host_state *state = talloc_get_type(c->private_data, struct host_state);
struct in_addr ip;
const char *address;
/* this is the blocking call we are going to lots of trouble
to avoid in the parent */
ip = interpret_addr2(state->name.name);
address = inet_ntoa(ip);
if (address != NULL) {
write(fd, address, strlen(address)+1);
}
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 host_state *state = talloc_get_type(c->private_data, struct host_state);
char address[128];
int ret;
pid_t child = state->child;
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;
if (strcmp(address, "0.0.0.0") == 0 ||
inet_addr(address) == INADDR_NONE) {
composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND);
return;
}
state->reply_addr = talloc_strdup(state, address);
if (composite_nomem(state->reply_addr, c)) return;
composite_done(c);
}
/*
gethostbyname name resolution method - async send
*/
struct composite_context *resolve_name_host_send(TALLOC_CTX *mem_ctx,
struct event_context *event_ctx,
void *privdata,
struct nbt_name *name)
{
struct composite_context *c;
struct host_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(c, struct host_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->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 gethostbyname() 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]);
run_child(c, fd[1]);
_exit(0);
}
close(fd[1]);
/* cleanup wayward children */
talloc_set_destructor(state, host_destructor);
return c;
}
/*
gethostbyname name resolution method - recv side
*/
NTSTATUS resolve_name_host_recv(struct composite_context *c,
TALLOC_CTX *mem_ctx, const char **reply_addr)
{
NTSTATUS status;
status = composite_wait(c);
if (NT_STATUS_IS_OK(status)) {
struct host_state *state = talloc_get_type(c->private_data, struct host_state);
*reply_addr = talloc_steal(mem_ctx, state->reply_addr);
}
talloc_free(c);
return status;
}
/*
gethostbyname name resolution method - sync call
*/
NTSTATUS resolve_name_host(struct nbt_name *name,
TALLOC_CTX *mem_ctx,
const char **reply_addr)
{
struct composite_context *c = resolve_name_host_send(mem_ctx, NULL, NULL, name);
return resolve_name_host_recv(c, mem_ctx, reply_addr);
}
bool resolve_context_add_host_method(struct resolve_context *ctx)
{
return resolve_context_add_method(ctx, resolve_name_host_send, resolve_name_host_recv,
NULL);
}
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