From 9492f0f00fd7c1815959f19988f83accce108ce4 Mon Sep 17 00:00:00 2001 From: Stefan Metzmacher Date: Fri, 12 Dec 2008 15:15:21 +0100 Subject: s4:libcli/resolve: add getaddrinfo()/dns_looup() resolving This "dns_ex" module provides flexible lookup methods for dns lookups. The getaddrinfo() part looks at /etc/hosts and dns. As it handles CNAME replies badly we fallback to use dns_lookup(name, "A"). The dns_lookup() makes DNS SRV lookups possible. This module is not a real resolve module, it's just a generic helper as the nbtlist.c code is. The next step will be that the "host" module will use the dns_ex.c code. metze --- source4/libcli/config.mk | 1 + source4/libcli/resolve/dns_ex.c | 484 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 485 insertions(+) create mode 100644 source4/libcli/resolve/dns_ex.c (limited to 'source4') diff --git a/source4/libcli/config.mk b/source4/libcli/config.mk index 8c31077d8c..b60cda9adf 100644 --- a/source4/libcli/config.mk +++ b/source4/libcli/config.mk @@ -136,6 +136,7 @@ PRIVATE_DEPENDENCIES = LIBCLI_NBT LIBSAMBA-HOSTCONFIG LIBNETIF LP_RESOLVE_OBJ_FILES = $(addprefix $(libclisrcdir)/resolve/, \ bcast.o nbtlist.o wins.o \ + dns_ex.o \ host.o resolve_lp.o) $(eval $(call proto_header_template,$(libclisrcdir)/resolve/lp_proto.h,$(LP_RESOLVE_OBJ_FILES:.o=.c))) diff --git a/source4/libcli/resolve/dns_ex.c b/source4/libcli/resolve/dns_ex.c new file mode 100644 index 0000000000..4bcf50a014 --- /dev/null +++ b/source4/libcli/resolve/dns_ex.c @@ -0,0 +1,484 @@ +/* + Unix SMB/CIFS implementation. + + async getaddrinfo()/dns_lookup() name resolution module + + Copyright (C) Andrew Tridgell 2005 + Copyright (C) Stefan Metzmacher 2008 + + 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 . +*/ + +/* + this module uses a fork() per getaddrinfo() or dns_looup() 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 librar (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 "lib/socket/socket.h" +#include "libcli/composite/composite.h" +#include "librpc/gen_ndr/ndr_nbt.h" +#include "libcli/resolve/resolve.h" +#include "heimdal/lib/roken/resolve.h" + +struct dns_ex_state { + bool do_getaddrinfo; + bool do_fallback; + bool do_srv; + struct nbt_name name; + struct socket_address **addrs; + 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 dns_ex_destructor(struct dns_ex_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_dns_lookup(struct dns_ex_state *state, int fd) +{ + struct dns_reply *reply; + struct resource_record *rr; + uint32_t count = 0; + uint32_t srv_valid = 0; + struct resource_record **srv_rr; + uint32_t addrs_valid = 0; + struct resource_record **addrs_rr; + char *addrs; + bool first; + uint32_t i; + + /* this is the blocking call we are going to lots of trouble + to avoid in the parent */ + reply = dns_lookup(state->name.name, state->do_srv?"SRV":"A"); + if (!reply) { + goto done; + } + + if (state->do_srv) { + dns_srv_order(reply); + } + + /* Loop over all returned records and pick the "srv" records */ + for (rr=reply->head; rr; rr=rr->next) { + /* we are only interested in the IN class */ + if (rr->class != C_IN) { + continue; + } + + if (state->do_srv) { + /* we are only interested in SRV records */ + if (rr->type != T_SRV) { + continue; + } + + /* verify we actually have a SRV record here */ + if (!rr->u.srv) { + continue; + } + + /* Verify we got a port */ + if (rr->u.srv->port == 0) { + continue; + } + } else { + /* we are only interested in A records */ + /* TODO: add AAAA support */ + if (rr->type != T_A) { + continue; + } + + /* verify we actually have a A record here */ + if (!rr->u.a) { + continue; + } + } + count++; + } + + if (count == 0) { + goto done; + } + + srv_rr = talloc_zero_array(state, + struct resource_record *, + count); + if (!srv_rr) { + goto done; + } + + addrs_rr = talloc_zero_array(state, + struct resource_record *, + count); + if (!addrs_rr) { + goto done; + } + + /* Loop over all returned records and pick the records */ + for (rr=reply->head;rr;rr=rr->next) { + /* we are only interested in the IN class */ + if (rr->class != C_IN) { + continue; + } + + if (state->do_srv) { + /* we are only interested in SRV records */ + if (rr->type != T_SRV) { + continue; + } + + /* verify we actually have a srv record here */ + if (!rr->u.srv) { + continue; + } + + /* Verify we got a port */ + if (rr->u.srv->port == 0) { + continue; + } + + srv_rr[srv_valid] = rr; + srv_valid++; + } else { + /* we are only interested in A records */ + /* TODO: add AAAA support */ + if (rr->type != T_A) { + continue; + } + + /* verify we actually have a A record here */ + if (!rr->u.a) { + continue; + } + + addrs_rr[addrs_valid] = rr; + addrs_valid++; + } + } + + for (i=0; i < srv_valid; i++) { + for (rr=reply->head;rr;rr=rr->next) { + + if (rr->class != C_IN) { + continue; + } + + /* we are only interested in SRV records */ + if (rr->type != T_A) { + continue; + } + + /* verify we actually have a srv record here */ + if (strcmp(&srv_rr[i]->u.srv->target[0], rr->domain) != 0) { + continue; + } + + addrs_rr[i] = rr; + addrs_valid++; + break; + } + } + + if (addrs_valid == 0) { + goto done; + } + + addrs = talloc_strdup(state, ""); + if (!addrs) { + goto done; + } + first = true; + for (i=0; i < count; i++) { + if (!addrs_rr[i]) { + continue; + } + addrs = talloc_asprintf_append_buffer(addrs, "%s%s:%u", + first?"":",", + inet_ntoa(*addrs_rr[i]->u.a), + srv_rr[i]?srv_rr[i]->u.srv->port:0); + if (!addrs) { + goto done; + } + first = false; + } + + if (addrs) { + write(fd, addrs, talloc_get_size(addrs)); + } + +done: + close(fd); +} + +/* + the blocking child +*/ +static void run_child_getaddrinfo(struct dns_ex_state *state, int fd) +{ + int ret; + struct addrinfo hints; + struct addrinfo *res; + struct addrinfo *res_list = NULL; + char *addrs; + bool first; + + ZERO_STRUCT(hints); + hints.ai_socktype = SOCK_STREAM; + hints.ai_family = AF_INET;/* TODO: add AF_INET6 support */ + hints.ai_flags = AI_ADDRCONFIG | AI_NUMERICSERV; + + ret = getaddrinfo(state->name.name, "0", &hints, &res_list); + if (ret == EAI_NODATA && state->do_fallback) { + /* getaddrinfo() doesn't handle CNAME records */ + run_child_dns_lookup(state, fd); + return; + } + if (ret != 0) { + goto done; + } + + addrs = talloc_strdup(state, ""); + if (!addrs) { + goto done; + } + first = true; + for (res = res_list; res; res = res->ai_next) { + struct sockaddr_in *in; + + if (res->ai_family != AF_INET) { + continue; + } + in = (struct sockaddr_in *)res->ai_addr; + + addrs = talloc_asprintf_append_buffer(addrs, "%s%s:%u", + first?"":",", + inet_ntoa(in->sin_addr), + 0); + if (!addrs) { + goto done; + } + first = false; + } + + if (addrs) { + write(fd, addrs, talloc_get_size(addrs)); + } +done: + if (res_list) { + freeaddrinfo(res_list); + } + 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 dns_ex_state *state = talloc_get_type(c->private_data, + struct dns_ex_state); + char address[2048]; + uint32_t num_addrs, i; + char **addrs; + int ret; + 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; + + addrs = str_list_make(state, address, ","); + if (composite_nomem(addrs, c)) return; + + num_addrs = str_list_length((const char * const *)addrs); + + state->addrs = talloc_array(state, struct socket_address *, + num_addrs+1); + if (composite_nomem(state->addrs, c)) return; + + for (i=0; i < num_addrs; i++) { + uint32_t port = 0; + char *p = strrchr(addrs[i], ':'); + + if (!p) { + composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND); + return; + } + + *p = '\0'; + p++; + + if (strcmp(addrs[i], "0.0.0.0") == 0 || + inet_addr(addrs[i]) == INADDR_NONE) { + composite_error(c, NT_STATUS_OBJECT_NAME_NOT_FOUND); + return; + } + port = strtoul(p, NULL, 10); + if (port > UINT16_MAX) { + port = 0; + } + state->addrs[i] = socket_address_from_strings(state->addrs, + "ipv4", + addrs[i], + port); + if (composite_nomem(state->addrs[i], c)) return; + } + state->addrs[i] = NULL; + + composite_done(c); +} + +/* + getaddrinfo() or dns_lookup() name resolution method - async send + */ +struct composite_context *resolve_name_dns_ex_send(TALLOC_CTX *mem_ctx, + struct event_context *event_ctx, + void *privdata, + struct nbt_name *name, + bool do_getaddrinfo, + bool do_fallback, + bool do_srv) +{ + struct composite_context *c; + struct dns_ex_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_zero(c, struct dns_ex_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->do_getaddrinfo = do_getaddrinfo; + state->do_fallback = do_fallback; + state->do_srv = do_srv; + + 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 dns_lookup() 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]); + if (state->do_getaddrinfo) { + run_child_getaddrinfo(state, fd[1]); + } else { + run_child_dns_lookup(state, fd[1]); + } + _exit(0); + } + close(fd[1]); + + /* cleanup wayward children */ + talloc_set_destructor(state, dns_ex_destructor); + + return c; +} + +/* + getaddrinfo() or dns_lookup() name resolution method - recv side +*/ +NTSTATUS resolve_name_dns_ex_recv(struct composite_context *c, + TALLOC_CTX *mem_ctx, + struct socket_address ***addrs) +{ + NTSTATUS status; + + status = composite_wait(c); + + if (NT_STATUS_IS_OK(status)) { + struct dns_ex_state *state = talloc_get_type(c->private_data, + struct dns_ex_state); + *addrs = talloc_steal(mem_ctx, state->addrs); + } + + talloc_free(c); + return status; +} -- cgit