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Add support for "custom" DNS servers to be used in address resolution 

Use the C-ARES ares_set_servers() API to set a list of DNS servers to use.
The list of DNS servers is controlled through a UAT. There is also a boolean
preference to determine if the custom list should be used.  The boolean preference
was added to arbitrate between the "default" list of servers that C-ARES creates
during initialization and using the "custom" list (which may be empty and we don't
want the "default" list to be overwritten)

Bug: 15960
Change-Id: I4ba071777f6bb9bc2fef313b7618908d805c0690
Reviewed-on: https://code.wireshark.org/review/34419
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>
Reviewed-by: Michael Mann <mmann78@netscape.net>
This commit is contained in:
Michael Mann 2019-09-01 12:02:27 -04:00
parent 6d6376e81f
commit c556f307c9
3 changed files with 143 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

141
epan/addr_resolv.c
View File

@ -94,6 +94,7 @@
#include <epan/to_str-int.h>
#include <epan/maxmind_db.h>
#include <epan/prefs.h>
#include <epan/uat.h>
#define ENAME_HOSTS "hosts"
#define ENAME_SUBNETS "subnets"
@ -365,6 +366,52 @@ static gboolean async_dns_initialized = FALSE;
static guint async_dns_in_flight = 0;
static wmem_list_t *async_dns_queue_head = NULL;
//UAT for providing a list of DNS servers to C-ARES for name resolution
gboolean use_custom_dns_server_list = FALSE;
struct dns_server_data {
char *ipaddr;
};
UAT_CSTRING_CB_DEF(dnsserverlist_uats, ipaddr, struct dns_server_data)
static uat_t *dnsserver_uat = NULL;
static struct dns_server_data *dnsserverlist_uats = NULL;
static guint ndnsservers = 0;
static void
dns_server_free_cb(void *data)
{
struct dns_server_data *h = (struct dns_server_data*)data;
g_free(h->ipaddr);
}
static void*
dns_server_copy_cb(void *dst_, const void *src_, size_t len _U_)
{
const struct dns_server_data *src = (const struct dns_server_data *)src_;
struct dns_server_data *dst = (struct dns_server_data *)dst_;
dst->ipaddr = g_strdup(src->ipaddr);
return dst;
}
static gboolean
dnsserver_uat_fld_ip_chk_cb(void* r _U_, const char* ipaddr, guint len _U_, const void* u1 _U_, const void* u2 _U_, char** err)
{
//Check for a valid IPv4 or IPv6 address.
if (ipaddr && g_hostname_is_ip_address(ipaddr)) {
*err = NULL;
return TRUE;
}
*err = g_strdup_printf("No valid IP address given.");
return FALSE;
}
static void
c_ares_ghba_sync_cb(void *arg, int status, int timeouts _U_, struct hostent *he) {
sync_dns_data_t *sdd = (sync_dns_data_t *)arg;
@ -504,6 +551,63 @@ set_resolution_synchrony(gboolean synchronous)
{
resolve_synchronously = synchronous;
}
static void
c_ares_set_dns_servers(void)
{
if ((!async_dns_initialized) || (!use_custom_dns_server_list))
return;
if (ndnsservers == 0) {
//clear the list of servers. This may effectively disable name resolution
ares_set_servers(ghba_chan, NULL);
ares_set_servers(ghbn_chan, NULL);
} else {
struct ares_addr_node* servers = wmem_alloc_array(NULL, struct ares_addr_node, ndnsservers);
ws_in4_addr ipv4addr;
ws_in6_addr ipv6addr;
gboolean invalid_IP_found = FALSE;
struct ares_addr_node* server;
guint i;
for (i = 0, server = servers; i < ndnsservers-1; i++, server++) {
if (ws_inet_pton6(dnsserverlist_uats[i].ipaddr, &ipv6addr)) {
server->family = AF_INET6;
memcpy(&server->addr.addr6, &ipv6addr, 16);
} else if (ws_inet_pton4(dnsserverlist_uats[i].ipaddr, &ipv4addr)) {
server->family = AF_INET;
memcpy(&server->addr.addr4, &ipv4addr, 4);
} else {
//This shouldn't happen, but just in case...
invalid_IP_found = TRUE;
server->family = 0;
memset(&server->addr.addr4, 0, 4);
break;
}
server->next = (server+1);
}
if (!invalid_IP_found) {
if (ws_inet_pton6(dnsserverlist_uats[i].ipaddr, &ipv6addr)) {
server->family = AF_INET6;
memcpy(&server->addr.addr6, &ipv6addr, 16);
}
else if (ws_inet_pton4(dnsserverlist_uats[i].ipaddr, &ipv4addr)) {
server->family = AF_INET;
memcpy(&server->addr.addr4, &ipv4addr, 4);
} else {
//This shouldn't happen, but just in case...
server->family = 0;
memset(&server->addr.addr4, 0, 4);
}
}
server->next = NULL;
ares_set_servers(ghba_chan, servers);
ares_set_servers(ghbn_chan, servers);
wmem_free(NULL, servers);
}
}
#else
void
set_resolution_synchrony(gboolean synchronous _U_)
@ -2692,6 +2796,35 @@ addr_resolve_pref_init(module_t *nameres)
" is enabled.",
&gbl_resolv_flags.use_external_net_name_resolver);
prefs_register_bool_preference(nameres, "use_custom_dns_servers",
"Use custom list of DNS servers for name resolution",
"Uses DNS Servers list to resolve network names if TRUE. If FALSE, default information is used",
&use_custom_dns_server_list);
static uat_field_t dns_server_uats_flds[] = {
UAT_FLD_CSTRING_OTHER(dnsserverlist_uats, ipaddr, "IP address", dnsserver_uat_fld_ip_chk_cb, "IPv4 or IPv6 address"),
UAT_END_FIELDS
};
dnsserver_uat = uat_new("DNS Servers",
sizeof(struct dns_server_data),
"addr_resolve_dns_servers", /* filename */
TRUE, /* from_profile */
&dnsserverlist_uats, /* data_ptr */
&ndnsservers, /* numitems_ptr */
UAT_AFFECTS_DISSECTION,
NULL,
dns_server_copy_cb,
NULL,
dns_server_free_cb,
c_ares_set_dns_servers,
NULL,
dns_server_uats_flds);
prefs_register_uat_preference(nameres, "dns_servers",
"DNS Servers",
"A table of IPv4 and IPv6 addresses that will be used resolve IP names and addresses",
dnsserver_uat);
prefs_register_obsolete_preference(nameres, "concurrent_dns");
prefs_register_uint_preference(nameres, "name_resolve_concurrency",
@ -2731,6 +2864,13 @@ addr_resolve_pref_init(module_t *nameres)
}
void addr_resolve_pref_apply(void)
{
#ifdef HAVE_C_ARES
c_ares_set_dns_servers();
#endif
}
void
disable_name_resolution(void) {
gbl_resolv_flags.mac_name = FALSE;
@ -2995,6 +3135,7 @@ host_name_lookup_init(void)
#endif
if (ares_init(&ghba_chan) == ARES_SUCCESS && ares_init(&ghbn_chan) == ARES_SUCCESS) {
async_dns_initialized = TRUE;
c_ares_set_dns_servers();
}
#ifdef CARES_HAVE_ARES_LIBRARY_INIT
}

1
epan/addr_resolv.h
View File

@ -174,6 +174,7 @@ WS_DLL_PUBLIC int port_with_resolution_to_str_buf(gchar *buf, gulong buf_size,
/* Setup name resolution preferences */
struct pref_module;
extern void addr_resolve_pref_init(struct pref_module *nameres);
extern void addr_resolve_pref_apply(void);
/*
* disable_name_resolution() sets all relevant gbl_resolv_flags to FALSE.

2
epan/prefs.c
View File

@ -3535,7 +3535,7 @@ prefs_register_modules(void)
/* Name Resolution */
nameres_module = prefs_register_module(NULL, "nameres", "Name Resolution",
"Name Resolution", NULL, TRUE);
"Name Resolution", addr_resolve_pref_apply, TRUE);
addr_resolve_pref_init(nameres_module);
oid_pref_init(nameres_module);
maxmind_db_pref_init(nameres_module);