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Remove 'dns_resolver' option, replace w/ ZEEK_DNS_RESOLVER env. var.

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The later simply doesn't work well in conjunction with hostname
literals.  i.e. "google.com" (without quotes) needs to be resolved
to a set of addresses at parse-time, so if a user wishes to use a
custom resolver, we need that to be configured independently from
the order in which scripts get parsed.  Configuring 'dns_resolver'
via scripting "redef" is clearly dependent on parse order.

Note 'dns_resolver' hasn't been in any release version yet, so
I'm removing it outright, no deprecation.  The ZEEK_DNS_RESOLVER
environment variable now serves the original purpose.
This commit is contained in:
Jon Siwek 2019-04-29 18:09:29 -07:00
parent 49908ac865
commit f7c1cde7c7
5 changed files with 29 additions and 36 deletions
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2
doc

@ -1 +1 @@
Subproject commit 073bb08473b8172b8bb175e0702204f15f522392
Subproject commit 856db2bb4014d15a94cb336d7e5e8ca1d4627b1e

6
scripts/base/init-bare.zeek
View file

@ -3743,12 +3743,6 @@ global dns_skip_all_addl = T &redef;
## traffic and do not process it. Set to 0 to turn off this functionality.
global dns_max_queries = 25 &redef;
## The address of the DNS resolver to use. If not changed from the
## unspecified address, ``[::]``, the first nameserver from /etc/resolv.conf
## gets used (IPv6 is currently only supported if set via this option, not
## when parsed from the file).
const dns_resolver = [::] &redef;
## HTTP session statistics.
##
## .. zeek:see:: http_stats

45
src/DNS_Mgr.cc
View file

@ -388,6 +388,7 @@ DNS_Mgr::DNS_Mgr(DNS_MgrMode arg_mode)
num_requests = 0;
successful = 0;
failed = 0;
nb_dns = nullptr;
}
DNS_Mgr::~DNS_Mgr()
@ -399,16 +400,21 @@ DNS_Mgr::~DNS_Mgr()
delete [] dir;
}
void DNS_Mgr::InitPostScript()
void DNS_Mgr::Init()
{
if ( did_init )
return;
auto dns_resolver_id = global_scope()->Lookup("dns_resolver");
auto dns_resolver_addr = dns_resolver_id->ID_Val()->AsAddr();
// Note that Init() may be called by way of LookupHost() during the act of
// parsing a hostname literal (e.g. google.com), so we can't use a
// script-layer option to configure the DNS resolver as it may not be
// configured to the user's desired address at the time when we need to to
// the lookup.
auto dns_resolver = getenv("ZEEK_DNS_RESOLVER");
auto dns_resolver_addr = dns_resolver ? IPAddr(dns_resolver) : IPAddr();
char err[NB_DNS_ERRSIZE];
if ( dns_resolver_addr == IPAddr("::") )
if ( dns_resolver_addr == IPAddr() )
nb_dns = nb_dns_init(err);
else
{
@ -433,19 +439,11 @@ void DNS_Mgr::InitPostScript()
if ( ! nb_dns )
reporter->Warning("problem initializing NB-DNS: %s", err);
const char* cache_dir = dir ? dir : ".";
if ( mode == DNS_PRIME && ! ensure_dir(cache_dir) )
{
did_init = 0;
return;
did_init = true;
}
cache_name = new char[strlen(cache_dir) + 64];
sprintf(cache_name, "%s/%s", cache_dir, ".bro-dns-cache");
LoadCache(fopen(cache_name, "r"));
void DNS_Mgr::InitPostScript()
{
dns_mapping_valid = internal_handler("dns_mapping_valid");
dns_mapping_unverified = internal_handler("dns_mapping_unverified");
dns_mapping_new_name = internal_handler("dns_mapping_new_name");
@ -455,14 +453,18 @@ void DNS_Mgr::InitPostScript()
dm_rec = internal_type("dns_mapping")->AsRecordType();
did_init = 1;
// Registering will call Init()
iosource_mgr->Register(this, true);
// We never set idle to false, having the main loop only calling us from
// time to time. If we're issuing more DNS requests than we can handle
// in this way, we are having problems anyway ...
SetIdle(true);
const char* cache_dir = dir ? dir : ".";
cache_name = new char[strlen(cache_dir) + 64];
sprintf(cache_name, "%s/%s", cache_dir, ".bro-dns-cache");
LoadCache(fopen(cache_name, "r"));
}
static TableVal* fake_name_lookup_result(const char* name)
@ -497,12 +499,11 @@ TableVal* DNS_Mgr::LookupHost(const char* name)
if ( mode == DNS_FAKE )
return fake_name_lookup_result(name);
Init();
if ( ! nb_dns )
return empty_addr_set();
if ( ! did_init )
Init();
if ( mode != DNS_PRIME )
{
HostMap::iterator it = host_mappings.find(name);
@ -553,7 +554,6 @@ TableVal* DNS_Mgr::LookupHost(const char* name)
Val* DNS_Mgr::LookupAddr(const IPAddr& addr)
{
if ( ! did_init )
Init();
if ( mode != DNS_PRIME )
@ -1072,7 +1072,6 @@ static void resolve_lookup_cb(DNS_Mgr::LookupCallback* callback,
void DNS_Mgr::AsyncLookupAddr(const IPAddr& host, LookupCallback* callback)
{
if ( ! did_init )
Init();
if ( mode == DNS_FAKE )
@ -1111,7 +1110,6 @@ void DNS_Mgr::AsyncLookupAddr(const IPAddr& host, LookupCallback* callback)
void DNS_Mgr::AsyncLookupName(const string& name, LookupCallback* callback)
{
if ( ! did_init )
Init();
if ( mode == DNS_FAKE )
@ -1150,7 +1148,6 @@ void DNS_Mgr::AsyncLookupName(const string& name, LookupCallback* callback)
void DNS_Mgr::AsyncLookupNameText(const string& name, LookupCallback* callback)
{
if ( ! did_init )
Init();
if ( mode == DNS_FAKE )

1
src/DNS_Mgr.h
View file

@ -136,6 +136,7 @@ protected:
iosource::FD_Set* except) override;
double NextTimestamp(double* network_time) override;
void Process() override;
void Init() override;
const char* Tag() override { return "DNS_Mgr"; }
DNS_MgrMode mode;

1
src/main.cc
View file

@ -215,6 +215,7 @@ void usage(int code = 1)
fprintf(stderr, " $BRO_LOG_SUFFIX | ASCII log file extension (.%s)\n", logging::writer::Ascii::LogExt().c_str());
fprintf(stderr, " $BRO_PROFILER_FILE | Output file for script execution statistics (not set)\n");
fprintf(stderr, " $BRO_DISABLE_BROXYGEN | Disable Zeexygen documentation support (%s)\n", getenv("BRO_DISABLE_BROXYGEN") ? "set" : "not set");
fprintf(stderr, " $ZEEK_DNS_RESOLVER | IPv4/IPv6 address of DNS resolver to use (%s)\n", getenv("ZEEK_DNS_RESOLVER") ? getenv("ZEEK_DNS_RESOLVER") : "not set, will use first IPv4 address from /etc/resolv.conf");
fprintf(stderr, "\n");