mirror of
https://github.com/samba-team/samba.git
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r4916: added "host" name resolution using fork() per gethostbyname()
comments welcome, but please think about the alternatives first :-)
This commit is contained in:
Andrew Tridgell
committed by
Gerald (Jerry) Carter
Gerald (Jerry) Carter
parent
b20c0561b8
commit
3d40b47990
233
source/libcli/resolve/host.c
Normal file
233
source/libcli/resolve/host.c
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@@ -0,0 +1,233 @@
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/*
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Unix SMB/CIFS implementation.
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async gethostbyname() name resolution module
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Copyright (C) Andrew Tridgell 2005
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/*
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this module uses a fork() per gethostbyname() call. At first that
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might seem crazy, but it is actually very fast, and solves many of
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the tricky problems of keeping a child hanging around in a library
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(like what happens when the parent forks). We use a talloc
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destructor to ensure that the child is cleaned up when we have
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finished with this name resolution.
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*/
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#include "includes.h"
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#include "events.h"
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#include "system/network.h"
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#include "libcli/raw/libcliraw.h"
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#include "libcli/composite/composite.h"
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struct host_state {
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struct nbt_name name;
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const char *reply_addr;
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pid_t child;
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int child_fd;
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struct fd_event *fde;
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struct event_context *event_ctx;
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};
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/*
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kill off a wayward child if needed. This allows us to stop an async
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name resolution without leaving a potentially blocking call running
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in a child
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*/
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static int host_destructor(void *ptr)
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{
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struct host_state *state = talloc_get_type(ptr, struct host_state);
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close(state->child_fd);
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if (state->child != (pid_t)-1) {
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kill(state->child, SIGTERM);
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}
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if (state->fde) {
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event_remove_fd(state->event_ctx, state->fde);
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}
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return 0;
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}
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/*
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the blocking child
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*/
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static void run_child(struct smbcli_composite *c, int fd)
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{
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struct host_state *state = talloc_get_type(c->private, struct host_state);
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struct ipv4_addr ip;
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const char *address;
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/* this is the blocking call we are going to lots of trouble
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to avoid in the parent */
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ip = interpret_addr2(state->name.name);
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address = sys_inet_ntoa(ip);
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if (address != NULL) {
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write(fd, address, strlen(address)+1);
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}
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}
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/*
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handle a read event on the pipe
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*/
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static void pipe_handler(struct event_context *ev, struct fd_event *fde,
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struct timeval t, uint16_t flags)
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{
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struct smbcli_composite *c = talloc_get_type(fde->private, struct smbcli_composite);
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struct host_state *state = talloc_get_type(c->private, struct host_state);
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char address[128];
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int ret;
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/* if we get any event from the child then we know that we
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won't need to kill it off */
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state->child = (pid_t)-1;
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/* yes, we don't care about EAGAIN or other niceities
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here. They just can't happen with this parent/child
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relationship, and even if they did then giving an error is
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the right thing to do */
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ret = read(state->child_fd, address, sizeof(address)-1);
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if (ret <= 0) goto failed;
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/* enusre the address looks good */
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address[ret] = 0;
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if (strcmp(address, "0.0.0.0") == 0 ||
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sys_inet_addr(address) == INADDR_NONE) {
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goto failed;
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}
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state->reply_addr = talloc_strdup(state, address);
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if (state->reply_addr == NULL) goto failed;
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c->status = NT_STATUS_OK;
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c->state = SMBCLI_REQUEST_DONE;
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if (c->async.fn) {
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c->async.fn(c);
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}
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return;
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failed:
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c->status = NT_STATUS_BAD_NETWORK_NAME;
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c->state = SMBCLI_REQUEST_ERROR;
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if (c->async.fn) {
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c->async.fn(c);
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}
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}
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/*
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gethostbyname name resolution method - async send
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*/
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struct smbcli_composite *resolve_name_host_send(struct nbt_name *name,
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struct event_context *event_ctx)
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{
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struct smbcli_composite *c;
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struct host_state *state;
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NTSTATUS status;
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int fd[2] = { -1, -1 };
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struct fd_event fde;
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int ret;
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c = talloc_zero(NULL, struct smbcli_composite);
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if (c == NULL) goto failed;
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state = talloc(c, struct host_state);
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if (state == NULL) goto failed;
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status = nbt_name_dup(state, name, &state->name);
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if (!NT_STATUS_IS_OK(status)) goto failed;
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c->state = SMBCLI_REQUEST_SEND;
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c->private = state;
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c->event_ctx = talloc_reference(c, event_ctx);
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/* setup a pipe to chat to our child */
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ret = pipe(fd);
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if (ret == -1) goto failed;
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state->child_fd = fd[0];
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state->event_ctx = c->event_ctx;
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/* we need to put the child in our event context so
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we know when the gethostbyname() has finished */
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fde.fd = state->child_fd;
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fde.flags = EVENT_FD_READ;
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fde.handler = pipe_handler;
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fde.private = c;
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state->fde = event_add_fd(c->event_ctx, &fde);
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if (state->fde == NULL) {
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close(fd[0]);
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close(fd[1]);
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goto failed;
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}
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/* signal handling in posix really sucks - doing this in a library
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affects the whole app, but what else to do?? */
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signal(SIGCHLD, SIG_IGN);
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state->child = fork();
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if (state->child == (pid_t)-1) {
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goto failed;
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}
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if (state->child == 0) {
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close(fd[0]);
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run_child(c, fd[1]);
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_exit(0);
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}
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close(fd[1]);
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/* cleanup wayward children */
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talloc_set_destructor(state, host_destructor);
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return c;
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failed:
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talloc_free(c);
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return NULL;
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}
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/*
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gethostbyname name resolution method - recv side
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*/
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NTSTATUS resolve_name_host_recv(struct smbcli_composite *c,
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TALLOC_CTX *mem_ctx, const char **reply_addr)
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{
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NTSTATUS status;
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status = smb_composite_wait(c);
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if (NT_STATUS_IS_OK(status)) {
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struct host_state *state = talloc_get_type(c->private, struct host_state);
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*reply_addr = talloc_steal(mem_ctx, state->reply_addr);
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}
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talloc_free(c);
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return status;
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}
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/*
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gethostbyname name resolution method - sync call
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*/
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NTSTATUS resolve_name_host(struct nbt_name *name,
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TALLOC_CTX *mem_ctx,
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const char **reply_addr)
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{
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struct smbcli_composite *c = resolve_name_host_send(name, NULL);
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return resolve_name_host_recv(c, mem_ctx, reply_addr);
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}
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@@ -33,6 +33,33 @@ struct resolve_state {
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static struct smbcli_composite *setup_next_method(struct smbcli_composite *c);
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/* pointers to the resolver backends */
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static const struct resolve_method {
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const char *name;
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struct smbcli_composite *(*send_fn)(struct nbt_name *, struct event_context *);
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NTSTATUS (*recv_fn)(struct smbcli_composite *, TALLOC_CTX *, const char **);
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} methods[] = {
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{ "bcast", resolve_name_bcast_send, resolve_name_bcast_recv },
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{ "wins", resolve_name_wins_send, resolve_name_wins_recv },
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{ "host", resolve_name_host_send, resolve_name_host_recv }
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};
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/*
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find a matching backend
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*/
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static const struct resolve_method *find_method(const char *name)
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{
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int i;
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if (name == NULL) return NULL;
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for (i=0;i<ARRAY_SIZE(methods);i++) {
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if (strcasecmp(name, methods[i].name) == 0) {
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return &methods[i];
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}
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}
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return NULL;
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}
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/*
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handle completion of one name resolve method
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*/
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@@ -40,15 +67,9 @@ static void resolve_handler(struct smbcli_composite *req)
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{
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struct smbcli_composite *c = req->async.private;
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struct resolve_state *state = talloc_get_type(c->private, struct resolve_state);
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const char *method = state->methods[0];
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const struct resolve_method *method = find_method(state->methods[0]);
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if (strcasecmp(method, "bcast")) {
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c->status = resolve_name_bcast_recv(req, state, &state->reply_addr);
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} else if (strcasecmp(method, "wins")) {
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c->status = resolve_name_wins_recv(req, state, &state->reply_addr);
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} else {
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c->status = NT_STATUS_INTERNAL_ERROR;
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}
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c->status = method->recv_fn(req, state, &state->reply_addr);
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if (!NT_STATUS_IS_OK(c->status)) {
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state->methods++;
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@@ -72,18 +93,16 @@ static void resolve_handler(struct smbcli_composite *req)
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static struct smbcli_composite *setup_next_method(struct smbcli_composite *c)
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{
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struct resolve_state *state = talloc_get_type(c->private, struct resolve_state);
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const char *method;
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struct smbcli_composite *req = NULL;
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do {
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method = state->methods[0];
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if (method == NULL) break;
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if (strcasecmp(method, "bcast")) {
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req = resolve_name_bcast_send(&state->name, c->event_ctx);
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} else if (strcasecmp(method, "wins")) {
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req = resolve_name_wins_send(&state->name, c->event_ctx);
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const struct resolve_method *method = find_method(state->methods[0]);
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if (method) {
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req = method->send_fn(&state->name, c->event_ctx);
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if (req == NULL) {
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state->methods++;
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}
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}
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if (req == NULL) state->methods++;
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} while (!req && state->methods[0]);
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if (req) {
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