/* 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 2 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, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ /* 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/raw/libcliraw.h" #include "libcli/composite/composite.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(void *ptr) { struct host_state *state = talloc_get_type(ptr, struct host_state); close(state->child_fd); if (state->child != (pid_t)-1) { kill(state->child, SIGTERM); } return 0; } /* the blocking child */ static void run_child(struct composite_context *c, int fd) { struct host_state *state = talloc_get_type(c->private, struct host_state); struct ipv4_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 = sys_inet_ntoa(ip); if (address != NULL) { write(fd, address, strlen(address)+1); } } /* handle a read event on the pipe */ static void pipe_handler(struct event_context *ev, struct fd_event *fde, uint16_t flags, void *private) { struct composite_context *c = talloc_get_type(private, struct composite_context); struct host_state *state = talloc_get_type(c->private, struct host_state); char address[128]; int ret; /* if we get any event from the child then we know that we won't need to kill it off */ state->child = (pid_t)-1; /* 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); if (ret <= 0) goto failed; /* enusre the address looks good */ address[ret] = 0; if (strcmp(address, "0.0.0.0") == 0 || sys_inet_addr(address) == INADDR_NONE) { goto failed; } state->reply_addr = talloc_strdup(state, address); if (state->reply_addr == NULL) goto failed; c->status = NT_STATUS_OK; c->state = SMBCLI_REQUEST_DONE; if (c->async.fn) { c->async.fn(c); } return; failed: c->status = NT_STATUS_BAD_NETWORK_NAME; c->state = SMBCLI_REQUEST_ERROR; if (c->async.fn) { c->async.fn(c); } } /* gethostbyname name resolution method - async send */ struct composite_context *resolve_name_host_send(struct nbt_name *name, struct event_context *event_ctx) { struct composite_context *c; struct host_state *state; NTSTATUS status; int fd[2] = { -1, -1 }; int ret; c = talloc_zero(NULL, struct composite_context); if (c == NULL) goto failed; state = talloc(c, struct host_state); if (state == NULL) goto failed; status = nbt_name_dup(state, name, &state->name); if (!NT_STATUS_IS_OK(status)) goto failed; c->state = SMBCLI_REQUEST_SEND; c->private = state; c->event_ctx = talloc_reference(c, event_ctx); /* setup a pipe to chat to our child */ ret = pipe(fd); if (ret == -1) goto failed; 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 (state->fde == NULL) { close(fd[0]); close(fd[1]); goto failed; } /* signal handling in posix really sucks - doing this in a library affects the whole app, but what else to do?? */ signal(SIGCHLD, SIG_IGN); state->child = fork(); if (state->child == (pid_t)-1) { goto failed; } 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; failed: talloc_free(c); return NULL; } /* 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, 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(name, NULL); return resolve_name_host_recv(c, mem_ctx, reply_addr); }