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Dns.cpp
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Dns.cpp
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#include "gb-include.h"
#include "Dns.h"
#include "HashTableT.h"
//#include "Threads.h"
// comment out the following line to disable DNS TLD caching
// TLD caching seems to give about 15% performance increase over not caching.
// it has been pretty thoroughly tested, but if there is a problem,
// feel free to disable it.
#define DNS_TLD_CACHE
// See section 7. RESOLVER IMPLEMENTATION in the rfc 1035
// TODO: use the canonical name as a normalization!!
// a global class extern'd in .h file
Dns g_dns;
RdbCache g_timedoutCache;
static int64_t s_antiLockCount = 1LL;
#define TIMEOUT_SINGLE_HOST 30
#define TIMEOUT_TOTAL 90
static void gotIpWrapper ( void *state , UdpSlot *slot ) ;
static void gotIpOfDNSWrapper ( void *state , int32_t ip ) ;
static void returnIp ( DnsState *ds , int32_t ip ) ;
// CallbackEntry now defined in HashTableT.cpp
static HashTableT<int64_t,CallbackEntry> s_dnstable;
static HashTableT<uint32_t,TLDIPEntry> s_TLDIPtable;
Dns::Dns() {
m_ips = NULL;
m_keys = NULL;
m_numSlots = 0;
}
// reset the udp server and rdb cache
void Dns::reset() {
log("db: resetting dns");
m_udpServer.reset();
m_rdbCache.reset();
g_timedoutCache.reset();
s_dnstable.reset();
s_TLDIPtable.reset();
m_rdbCacheLocal.reset();
// free hash table of /etc/hosts
if ( m_ips ) mfree ( m_ips , m_numSlots*4 , "Dns");
if ( m_keys ) mfree ( m_keys , m_numSlots*sizeof(key_t), "Dns");
m_ips = NULL;
m_keys = NULL;
m_numSlots = 0;
}
// . port will be incremented if already in use
// . use 1 socket for recving and sending
// . we can use a shared rdb cache
// . we use the dbId to separate our cache entries from other db's entries
bool Dns::init ( uint16_t clientPort ) {
// get primary dns server info from the conf class
m_dnsClientPort = clientPort; // g_conf.m_dnsClientPort;
// set the name of the cache. it will save to WORKDIR/{name}.dat
int32_t maxMem = g_conf.m_dnsMaxCacheMem ;
// . how many nodes in cache tree can we fit?
// . each rec is key (12) and ip(4)
// . overhead in cache is 56
// . that makes 56 + 4 = 60
// . not correct? stats suggest it's less than 25 bytes each
int32_t maxCacheNodes = maxMem / 25;
// make a copy of our protocol to pass to udp server
// static DnsProtocol proto;
// set the cache
if ( ! m_rdbCache.init ( maxMem ,
4 , // fixed data size of rec
false , // support lists of recs?
maxCacheNodes ,
false , // use half keys?
"dns" , // dbname
true )) // save cache to disk?
return log("dns: Cache init failed.");
// make a copy of our protocol to pass to udp server
// static DnsProtocol proto;
// set the cache
int32_t maxMemLocal = 100000;
if ( ! m_rdbCacheLocal.init ( maxMemLocal ,
4 , // fixed data size of rec
false , // support lists of recs?
maxMemLocal/25,
false , // use half keys?
"dnsLocal" , // dbname
true )) // save cache?
return log("dns: Cache local init failed.");
// . set the port, proto and hostmap in our udpServer
// . poll for timeouts every 11 seconds (11000 milliseconds)
if ( ! m_udpServer.init ( m_dnsClientPort,
&m_proto ,
1 ,// niceness
64000 ,// sock read buf
32000 ,// sock write buf
500 ,//polltime(.5secs)
500 ,//maxudpslots
true ))// is dns?
return log ("dns: Udp server init failed.");
// innocent log msg
log ( LOG_INIT,"dns: Sending requests on client port %"INT32" "
"using socket descriptor %i.",
(int32_t)m_dnsClientPort , m_udpServer.m_sock );
for ( int32_t i = 0 ; i < g_conf.m_numDns ; i++ ) {
if ( !g_conf.m_dnsIps[i] ) continue;
log ( LOG_INIT, "dns: Using nameserver %s:%i.",
iptoa(g_conf.m_dnsIps[i]) , g_conf.m_dnsPorts[i] );
}
// . only init the timedout cache once
// . cache the dns servers' ips who timeout on us so we don't slow
// things down. later we can turn this into a "speed" cache, so
// we ask the fastest servers first.
static bool s_init = false;
if ( s_init ) return true;
// just 30k for this little guy
int32_t maxCacheMem = 30000;
maxCacheNodes = maxCacheMem / 25;
g_timedoutCache.init ( maxCacheMem ,
4 , // fixed data size of rec
false , // support lists of recs?
maxCacheNodes ,
false , // use half keys?
"dnstimedout" , // dbname
true ); // save cache?
return true;
}
bool isTimedOut(int32_t ip) {
// is this ip address in the "timed out" cache. if so,
// then do not try again for at least 1 hour
char *rec;
int32_t recSize;
int32_t maxAge = 3600; // 1 hour in seconds
key_t k;
k.n0 = 0LL;
k.n1 = ip;
bool inCache = g_timedoutCache.getRecord ( (collnum_t)0 ,
k , // key
&rec ,
&recSize,
false ,//do copy?
maxAge ,
true );//inc cnt
return inCache;
}
inline bool parseTLD(DnsState* ds, char* buf, int32_t* len) {
// parse out the TLD
const char* hostname= ds->m_hostname;
const char* cbeg = hostname + gbstrlen(hostname);
const char* cend = cbeg;
bool found = false;
char* curs;
while (cbeg > hostname) {
if (*cbeg == '.') {
cbeg++;
found = true;
if (cend - cbeg > *len - 1)
return false;
*len = cend - cbeg;
gbmemcpy(buf, cbeg, *len);
buf[*len] = '\0';
for (curs = buf; *curs; curs++)
*curs = to_lower_a(*curs);
//log(LOG_DEBUG,"dns: parseTLD found '%s'", buf);
return true;
}
cbeg--;
}
return found;
}
inline uint32_t TLDIPKey(char* buf, int32_t len) {
// build "key" for TLD hash table
uint32_t key;
key = 0;
if (len > 4)
len = 4;
gbmemcpy(&key, buf, len);
return key;
}
#ifdef DNS_TLD_CACHE
// returns NULL if we had a TLD cache miss
// returns ptr if we had a TLD cache hit
// adjusts ds->m_depth and ds->m_dnsIps on a hit
static const TLDIPEntry* getTLDIP(DnsState* ds) {
//log(LOG_DEBUG, "dns: getTLDIP entry");
char buf[64];
int32_t len = sizeof(buf);
if (!parseTLD(ds, buf, &len)) {
log(LOG_WARN, "dns: unable to determine TLD for %s",
ds->m_hostname);
return NULL;
}
uint32_t key = TLDIPKey(buf, len);
if (key == 0) {
log(LOG_WARN, "dns: getTLDIP invalid key");
return NULL;
}
TLDIPEntry* tldip = s_TLDIPtable.getValuePointer(key);
if (tldip == NULL) {
//log(LOG_DEBUG, "dns: getTLDIP not in cache");
return NULL;
}
// JAB: 2038
if (tldip->expiry <= time(NULL)) {
log(LOG_DEBUG, "dns: getTLDIP expired for %s", ds->m_hostname);
return NULL;
}
log(LOG_DEBUG,"dns: TLD cache hit .%s NS depth %"INT32" for %s.",
buf, (int32_t) ds->m_depth, ds->m_hostname);
return tldip;
}
static void dumpTLDIP( const char* tld,
TLDIPEntry* tldip) {
for (int32_t i = 0; i < tldip->numTLDIPs; i++) {
log(LOG_DEBUG, "dns: .%s TLD IP %s",
tld, iptoa(tldip->TLDIP[i]));
}
}
static void setTLDIP( DnsState* ds,
TLDIPEntry* tldip) {
// see if it's already in cache (i.e. poss. expired).
const TLDIPEntry* cached = getTLDIP(ds);
int32_t now = time(NULL);
// expire TLD NS in 24 hours
tldip->expiry = now + 3600 * 24;
char buf[64];
int32_t len = sizeof(buf);
if (!parseTLD(ds, buf, &len)) {
log(LOG_WARN, "dns: unable to determine TLD for %s",
ds->m_hostname);
return;
}
char tld[64];
gbmemcpy(tld, buf, len);
tld[len] = '\0';
if (cached == NULL) {
uint32_t key = TLDIPKey(buf, len);
if (!s_TLDIPtable.addKey(key, *tldip)) {
log(LOG_WARN, "dns: unable to add %s to TLD cache",
ds->m_hostname);
return;
}
log(LOG_DEBUG, "dns: TLD .%s NS cache add", buf);
dumpTLDIP(tld, tldip);
}
else if (cached->expiry <= now) {
// JAB: non-const cast...
gbmemcpy((TLDIPEntry*) cached, tldip, sizeof(TLDIPEntry));
log(LOG_DEBUG, "dns: TLD .%s NS cache update", buf);
dumpTLDIP(tld, tldip);
}
else {
//log(LOG_DEBUG, "dns: TLD cache up-to-date");
}
}
#else // DNS_TLD_CACHE
// code that is run when TLDIP cache is disabled...
static const TLDIPEntry* getTLDIP(DnsState* ds) {
return NULL;
}
#endif // DNS_TLD_CACHE
// . returns true and sets g_errno on error
// . returns false if transaction blocked, true if completed
// . returns false if you must wait
// . calls gotIp with ip when it gets it or timesOut or errors out
// . sets *ip to 0 if none (does not exist)
// . sets *ip to -1 and sets g_errno if there was an error
bool Dns::getIp ( char *hostname ,
int32_t hostnameLen ,
int32_t *ip ,
void *state ,
void (* callback ) ( void *state , int32_t ip ) ,
DnsState *ds ,
//char **dnsNames ,
//int32_t numDnsNames ,
//int32_t *dnsIps ,
//int32_t numDnsIps ,
int32_t timeout ,
bool dnsLookup ,
// monitor.cpp passes in false for this:
bool cacheNotFounds ) {
// . don't accept large hostnames
// . technically the limit is 255 but i'm stricter
if ( hostnameLen >= 254 ) {
g_errno = EHOSTNAMETOOBIG;
log("dns: Asked to get IP of hostname over 253 "
"characters long.");
*ip=0;
return true;
}
// debug msg
char tmp[256];
gbmemcpy ( tmp , hostname , hostnameLen );
tmp [ hostnameLen ] = '\0';
log(LOG_DEBUG, "dns: hostname '%s'", tmp);
// assume no error
g_errno = 0;
// only g_dnsDistributed should be calling this, not g_dnsLocal
if ( this != &g_dns ) { char *xx = NULL; *xx = 0; }
// not thread safe
//if ( g_threads.amThread() ) { char *xx = NULL; *xx = 0; }
if ( hostnameLen <= 0 ) {
log(LOG_LOGIC,"dns: Asked to get IP of zero length hostname.");
*ip = 0;
return true;
}
// if url is already in a.b.c.d format return that
*ip = atoip ( hostname , hostnameLen );
if ( *ip != 0 ) {
log(LOG_DEBUG, "dns: IP address passed into getIp '%s'", tmp);
return true;
}
// key is hash of the hostname
key_t hostKey96 = hash96 ( hostname , hostnameLen );
// . is it in the /etc/hosts file?
// . BAD: could have a key collision!! TODO: fix..
if ( g_conf.m_useEtcHosts && isInFile ( hostKey96 , ip ) ) return true;
// . try getting from the cache first
// . this returns true if was in the cache and sets *ip to the ip
// . we now cached EDNSTIMEDOUT errors for a day, so *ip can be -1
// . TODO: watchout for key collision
if ( isInCache ( hostKey96 , ip ) ) {
// return 1 to indicate we got it right away in *ip
if ( ! g_conf.m_logDebugDns ) return true;
//char *dd = "distributed";
//if ( this == &g_dnsLocal ) dd = "local";
// debug msg
log(LOG_DEBUG,"dns: got ip of %s for %s in distributed cache.",
iptoa(*ip),tmp);
return true;
}
// . if this hostname request is already in progress, wait for that
// reply to to come back rather than launching a duplicate request.
// . each bucket in the s_dnstable hashtable is a possible head of a
// linked list of callback/state pairs which are waiting for that
// hostname's ip
// . is the ip for this hostname already being fetched?
// . if so, there will be a callback entry class that should match its
// DnsState::m_callback in there and have a key of key.n0 (see below)
// . TODO: we can have collisions and end up getting back the wrong ip
// how can we fix this? keep a ptr to ds->m_hostname? and if does
// not match then just error out?
int64_t hostKey64 = hostKey96.n0 & 0x7fffffffffffffffLL;
// never let this be zero
if ( hostKey64 == 0 ) hostKey64 = 1;
// see if we are already looking up this hostname
CallbackEntry *ptr = s_dnstable.getValuePointer ( hostKey64 );
// if he has our key see if his hostname matches ours, it should.
if ( ptr &&
// we do not store hostnameLen in ds, so make sure this is 0
! ptr->m_ds->m_hostname[hostnameLen] &&
(int32_t)gbstrlen(ptr->m_ds->m_hostname) == hostnameLen &&
strncmp ( ptr->m_ds->m_hostname, hostname, hostnameLen ) != 0 ) {
g_errno = EBADENGINEER;
log("dns: Found key collision in wait queue. host %s has "
"same key as %s. key=%"UINT64".",
ptr->m_ds->m_hostname, tmp, hostKey64);
//char *xx = NULL; *xx = 0;
// we should just error out if this happens, it is better
// than giving him the wrong ip, he will be retried later
// by the spider.
return true;
}
// regardless, add our "ce" to the table, but assume we are NOT first
// in line for a hostname and use a bogus key. it doesn't matter,
// we just need some memory to store our CallbackEntry class.
static int64_t s_bogus = 0;
// make a CallbackEntry class to add to a slot in the table
CallbackEntry ce;
ce.m_callback = callback;
ce.m_state = state;
ce.m_nextKey = 0LL; // assume we are the first for this hostname
ce.m_ds = NULL;
ce.m_listSize = 0;
// always inc now no matter what now so no danger of re-use
s_bogus++;
// if we are the first guy requesting the ip for this hostname
// then use "hostKey" to get the slot to store "ce",
int64_t finalKey = hostKey64 ;
// otherwise use "s_bogus" as the key. the bogus key is just for
// getting a slot to use to store "ce".
if ( ptr ) {
// let's hash it up for efficiency
finalKey = hash64 ( (char *)&s_bogus,8);
// never let this be 0
if ( finalKey == 0 ) finalKey = 1LL;
// bogus should never equal a key.n0 for any request, otherwise
// that is a collision. to avoid this possibility keep its hi
// bit set, and hi bit clear on the key.n0 key (hostKey). this
// way, a waiting slot can never collide with any other slot.
finalKey |= 0x8000000000000000LL;
}
// BUT if we are looking up a dns server's ip, then NEVER wait in
// line because we could deadlock!
if ( dnsLookup ) {
loop:
finalKey = hash64 ( hostKey64 , s_antiLockCount++ );
// it is not waiting in anyone's line, so turn this bit off
finalKey &= 0x7fffffffffffffffLL;
// ensure not 0
if ( finalKey == 0 ) finalKey = 1;
// assume hostKey is not in the table, even though it
// may be, we cannot wait in line behind it
ptr = NULL;
// ensure no collision, if so, s_antiLockCount will be
// different now so hash again until we do not collide
if ( s_dnstable.getValuePointer ( finalKey ) )
goto loop;
}
// assume we have no parent
int64_t parentKey = 0;
// if parent, set parentKey to "hostKey", the hash of the hostname
if ( ptr ) parentKey = hostKey64;
// make sure we do not have a circular dependency if we are looking
// up the ip of a dns in order to ask him the ip of what we are
// looking up.
// EXAMPLE:
// 1. get ip of xyz.com
// 2. have to ask dns1.xyz.com
// 3. to get his ip we have to ask dns2.xyz.com
// 4. and to get his ip we have to as dns1.xyz.com
// 5. which we'll see that it is already outstanding in the hashtable,
// i.e., it has a parent in there, and it will just wait in line
// never to get out of it, if it were not for the following circular
// dependency check:
// example url: www.hagener-schulen.de
int32_t loopCount = 0;
// loopCount is how many times we've had to ask for the ip of a
// nameserver recursively.
if ( ds ) loopCount = ds->m_loopCount;
// point to the current DnsState
char *parent = (char *)ds;
// the DnsState was built to hold a few DnsStates in it for just
// this purpose, so we can "backup" to our "parents" and make sure
// they did not initiate this linked list. Search for "ds2" below
// to see where we initiate the recursion.
while ( ptr && loopCount-- > 0 ) {
// the recursive "ds"es occupy DnsState::m_buf of their
// containing DnsState. go back one.
parent -= ((char *)ds->m_buf - (char *)ds);
// sanity check
//if ( ((DnsState *)parent)->m_buf != (char *)ds ) {
// char *xx = NULL; *xx = 0; }
// do we have the circular dependency?
if ( parent == (char *)ptr->m_ds ) {
g_errno = EBADENGINEER;
log(LOG_DEBUG,"dns: Caught circular dependency.");
return true;
}
}
// debug msg
log(LOG_DEBUG,"dns: Adding key %"UINT64" from table. "
"parentKey=%"UINT64" callback=%"PTRFMT" state=%"PTRFMT".",
finalKey,parentKey,(PTRTYPE)callback,(PTRTYPE)state);
// ensure "bogus" key not already present in table, otherwise,
// addKey will just overwrite the value!!
while ( ptr && s_dnstable.getValuePointer ( finalKey ) ) {
log("dns: Got collision on incremental key.");
finalKey += 1LL;
finalKey |= 0x8000000000000000LL;
}
// we need to be able to add ourselves to the table so our callback
// can get called, otherwise it is pointless. this returns false
// and sets g_errno on error.
int32_t slotNum = -1;
if ( ! s_dnstable.addKey ( finalKey , ce , &slotNum ) ) {
log("dns: Failed to add key to table: %s.",mstrerror(g_errno));
return true;
}
// get the value from the slot so we can insert into linked list.
CallbackEntry *ppp = s_dnstable.getValuePointerFromSlot ( slotNum );
// sanity check
if ( ppp->m_callback != callback || ppp->m_state != state ) {
log("dns: Failed sanity check 3.");
char *xx = NULL; *xx = 0;
}
// adding a key may have changed the parent ptr... get again just
// in case
if ( ptr ) {
ptr = s_dnstable.getValuePointer ( hostKey64 );
// sanity check - it should still be there for sure
if ( ! ptr ) { char *xx = NULL; *xx = 0; }
}
// . insert into beginning of the linked list to avoid having to scan
// . "ptr" is a ptr to the parent CallbackEntry, head of linked list
if ( ptr ) {
int64_t oldNext = ptr->m_nextKey;
ptr->m_nextKey = finalKey;
ppp->m_nextKey = oldNext;
// let parent know how big its linked list is
ptr->m_listSize++;
// propagate the list id, it is stored in the parent node
// so put it into us, too
ppp->m_listId = ptr->m_listId;
if ( g_conf.m_logDebugDns )
log(LOG_DEBUG,"dns: Waiting in line for %s. key=%"UINT64". "
"nextKey=%"UINT64" listSize=%"INT32" listId=%"INT32" "
"numSlots=%"INT32".",
tmp,finalKey,oldNext,
ptr->m_listSize,ptr->m_listId,
s_dnstable.getNumSlots());
// ok, we block now, waiting for the initial callback
return false;
}
// init our linked list size count
ppp->m_listSize = 1;
// it is the parent, use 0 to indicate none
static int32_t s_listId = 0;
ppp->m_listId = s_listId++;
// . make a DnsState
// . set g_errno and return true on malloc() error
if ( ds )
ds->m_freeit = false;
else {
ds = (DnsState *) mmalloc ( sizeof(DnsState ), "Dns" );
if ( ! ds ) {
log("dns: Failed to allocate mem for ip lookup.");
// debug msg
log(LOG_DEBUG,"dns: Removing2 key %"UINT64" from table. "
"parentKey=%"UINT64" callback=%"PTRFMT" state=%"PTRFMT".",
hostKey64,parentKey,
(PTRTYPE)callback,(PTRTYPE)state);
s_dnstable.removeKey ( finalKey );
return true;
}
ds->m_freeit = true;
// keep track of how many times we pluck out a DnsState
// from DnsState::m_buf.
ds->m_loopCount = 0;
ds->m_startTime = getTime();//time(NULL);//getTimeLocal();
}
// so monitor.cpp can avoid caching not founds or timeouts in case
// the network goes down on gk267
ds->m_cacheNotFounds = cacheNotFounds;
// set the ce.m_ds to our dns state so if a key collides later
// we can check DnsState::m_hostname. actually i think this is only
// used for sanity checking now.
ppp->m_ds = ds;
// reset this stuff
ds->m_numDnsIps [0] = 0;
ds->m_numDnsNames[0] = 0;
ds->m_depth = 0;
ds->m_numTried = 0;
ds->m_nameBufPtr = ds->m_nameBuf ;
ds->m_nameBufEnd = ds->m_nameBuf + 512;
ds->m_errno = 0;
ds->m_recursionDesired = 1;
// debug msg
//log("dns::getIp: %s (key=%"UINT64") NOT in cache...",tmp,key.n0);
// reset m_loopCount and startTime if we are just starting
if ( ds && callback != gotIpOfDNSWrapper ) {
ds->m_loopCount = 0;
ds->m_startTime = getTime();//time(NULL);//getTimeLocal();
}
// set caller callback info
// hostKey96 and finalKey are basically the same thing for hostnames
// that are NOT waiting in line. but finalKey is the lower 64 bits
// of hostKey96, but finalKey should have its hi bit cleared to
// indicate it is not waiting in line. Also, if looking up the IP
// of a dns, dnsLookup is true, and finalKey is hashed with a
// special count to give a unique hash because we can not have
// dnsLookups waiting in line because of deadlock issues.
// search for "dns A" below to see what i'm talking about.
ds->m_hostnameKey = hostKey96;
ds->m_tableKey = finalKey;
ds->m_this = this;
ds->m_state = state;
ds->m_callback = callback;
int32_t newlen = hostnameLen;
if ( newlen > 127 ) newlen = 127;
gbmemcpy ( ds->m_hostname , hostname , newlen );
ds->m_hostname [ newlen ] = '\0';
// copy the sendBuf cuz we need it in gotIp() to ensure hostnames match
//char *copy = (char *) mdup ( msg , msgSize , "Dns" );
//if ( ! copy ) {
// if ( ds->m_freeit ) mfree (ds,sizeof(DnsState),"Dns");
// return -1;
//}
// hack this for now
//int32_t numDns = 0;
//int32_t dnsIps[MAX_DNSIPS];
// copy the initial nameserver ips into ds->m_dnsIps[0] (depth 0)
if ( g_conf.m_askRootNameservers ) {
// ROOT TLD CACHE ATTEMPT GOES HERE...
// this will fill in depth 1 in the query,
// if we have the nameservers cached...
log(LOG_DEBUG,"dns: hostname %s", ds->m_hostname);
gbmemcpy(ds->m_dnsIps[0],g_conf.m_rnsIps, g_conf.m_numRns * 4);
ds->m_numDnsIps[0] = g_conf.m_numRns;
ds->m_numDnsNames[0] = 0;
ds->m_rootTLD[0] = true;
ds->m_fallbacks[0] = 0;
// if a TLD is cached, copy it to depth 1
const TLDIPEntry* tldip = getTLDIP(ds);
if (tldip) {
gbmemcpy( ds->m_dnsIps[1],
tldip->TLDIP,
tldip->numTLDIPs * sizeof(uint32_t));
ds->m_numDnsIps[1] = tldip->numTLDIPs;
ds->m_numDnsNames[1] = 0;
ds->m_rootTLD[1] = true;
ds->m_fallbacks[1] = 0;
ds->m_depth = 1;
}
}
// otherwise, use the local bind9 servers
else {
//gbmemcpy(ds->m_dnsIps[0],g_conf.m_dnsIps,g_conf.m_numDns * 4);
int32_t numDns = 0;
for ( int32_t i = 0; i < MAX_DNSIPS; i++ ) {
if ( g_conf.m_dnsIps[i] == 0 ) continue;
ds->m_dnsIps[0][numDns] = g_conf.m_dnsIps[i];
numDns++;
}
ds->m_numDnsIps[0] = numDns;
ds->m_numDnsNames[0] = 0;
ds->m_rootTLD[0] = false;
ds->m_fallbacks[0] = 0;
}
// return 0 if we block on the reply
//if ( ! sendToNextDNS ( ds , timeout ) ) return false;
// timeout from an individual dns is 20 seconds
if ( ! sendToNextDNS ( ds , TIMEOUT_SINGLE_HOST ) ) return false;
// debug msg
log(LOG_DEBUG,"dns: Removing3 key %"UINT64" from table. "
"parentKey=%"UINT64" callback=%"PTRFMT" state=%"PTRFMT".",
hostKey64,parentKey,
(PTRTYPE)callback,(PTRTYPE)state);
// if we made it here, remove from table
s_dnstable.removeKey ( finalKey ) ;
// should we free it
if ( ds->m_freeit ) mfree ( ds , sizeof(DnsState) ,"Dns" );
// ok, g_errno should still be set, return true as specified
return true;
}
// . returns false if blocked, sets g_errno and returns true otherwise
// . this is called by sendToNextDNS() when it has to get the ip of the DNS to
// send the request to.
bool Dns::getIpOfDNS ( DnsState *ds ) {
// bail if none
if ( ds->m_numDnsNames[ds->m_depth] <= 0 ) {
log(LOG_DEBUG, "dns: no dnsnames for '%s'",
ds->m_hostname);
return true;
}
// use the secondary ds for doing this
DnsState *ds2 = (DnsState *)ds->m_buf;
// do not keep getting the ip of the ns which may require us to get
// the ips of its ns, etc...
if ( ds->m_loopCount >= 3 ) {
addToCache ( ds->m_hostnameKey , -1 );
g_errno = EBADENGINEER;
log(LOG_INFO,"dns: Hit too many authority redirects for %s.",
ds->m_hostname);
return true;
}
// sanity check
if ( LOOP_BUF_SIZE / (sizeof(DnsState) - LOOP_BUF_SIZE) < 3 ) {
log("dns: Increase LOOP_BUF_SIZE, %"INT32", in Dns.h.",
(int32_t)LOOP_BUF_SIZE);
char *xx = NULL; *xx = 0;
}
// increment the loop count, we can only use m_buf so many times
// before running out of room.
ds2->m_loopCount = ds->m_loopCount + 1;
// set start time for timing out
ds2->m_startTime = ds->m_startTime;
// or if we have too many ips already, do not bother adding more
if (ds->m_numDnsIps[ds->m_depth]>=MAX_DNS_IPS){
log("dns: Already have %"INT32" ips at depth %"INT32".",
(int32_t)MAX_DNS_IPS,(int32_t)ds->m_depth);
g_errno=EBUFTOOSMALL;
return true;
}
// do not do this! this will break!
// int32_t n = ds->m_hostnameKey.n0 % numNames;
int32_t n = 0; // first is usually ns1, usually better
loop:
// get the name to get the ip for
int32_t depth = ds->m_depth;
int32_t numNames = ds->m_numDnsNames[depth];
char *hostname = ds->m_dnsNames[depth][n];
int32_t hostnameLen = gbstrlen(hostname);
int32_t ip = 0;
// loop over all dnsnames in case one causes a circular dependency
// . remove him from the array so we do not do him again
// . actually, this is not a guarantee, so we put a circular
// dependency check in getIP() above
ds->m_dnsNames [depth][n] = ds->m_dnsNames[depth][numNames-1];
ds->m_numDnsNames[depth]--;
//ds->m_numTried++;
//if (ds->m_numTried > .....
// debug note
log(LOG_DEBUG,"dns: Getting ip address of dns, %s for %s.",
hostname,ds->m_hostname);
// . returns -1 and sets g_errno on error
// . returns 0 if transaction blocked, 1 if completed
// . returns 0 if you must wait
// . calls gotIp with ip when it gets it or timesOut or errors out
// . set *ip to 0 if none (does not exist)
// . keep the timeout down to only 5 secs
// . do not set a mutual exclusion lock on ip lookups of dns servers
// in order to avoid having to lookups locking each other up. like
// . 1. we are getting the ip of dns A for resolve of hostname #1
// . 2. we are getting the ip of dns B for resolve of hostname #2
// . 3. dns A says to ask B and B says to ask A, we end up in
// a deadlock
if ( !g_dns.getIp ( hostname ,
hostnameLen ,
&ip ,
ds ,//state
gotIpOfDNSWrapper , //state,ip
ds2 ,
5 , // timeout
true )) { // dns lookup?
log(LOG_DEBUG, "dns: no block for getIp for '%s'", hostname);
return false;
}
// if that would cause a circulare dependency, try the next one
if ( g_errno == EBADENGINEER ) {
if ( ds->m_numDnsNames[depth] ) {
log("dns: looping in getIpOfDns for '%s'",
hostname);
goto loop;
}
else
log("dns: No names left to try after %s",hostname);
}
// did it have an error? g_errno will be set
// . if ip is 0 it was a does not exist
// . add it to the array of ips
if ( ip != 0 && ds->m_numDnsIps[depth] + 1 < MAX_DNS_IPS) {
if (isTimedOut(ip)) {
log(LOG_DEBUG,
"dns: Not adding [1] ip %s - timed out",
iptoa(ip));
}
else {
int32_t depth = ds->m_depth;
log(LOG_DEBUG,
"dns: Added ip [1-%"INT32"] %s to depth %"INT32" for %s.",
ds->m_numDnsIps[depth],
iptoa(ip),(int32_t)depth,ds->m_hostname);
ds->m_dnsIps[depth][ds->m_numDnsIps[depth]++] = ip ;
}
}
// we did not block
return true;
}
void gotIpOfDNSWrapper ( void *state , int32_t ip ) {
DnsState *ds = (DnsState *)state;
// log debug msg
//DnsState *ds2 = (DnsState *)ds->m_buf;
log(LOG_DEBUG,"dns: Got ip of dns %s for %s.",
iptoa(ip),ds->m_hostname);
// sanity check
if ( ds->m_numDnsIps[ds->m_depth] + 1 >= MAX_DNS_IPS ) {
log("dns: Wierd. Not enough buffer.");
char *xx = NULL; *xx = 0;
}
// . if ip is 0 it was a does not exist
// . add it to the array of ips
if ( ! g_errno && ip != 0 &&
ds->m_numDnsIps[ds->m_depth] + 1 < MAX_DNS_IPS) {
if (isTimedOut(ip)) {
log(LOG_DEBUG,
"dns: Not adding [2] ip %s - timed out",
iptoa(ip));
}
else {
int32_t depth = ds->m_depth;
ds->m_dnsIps[depth][ds->m_numDnsIps[depth]++] = ip ;
log(LOG_DEBUG,
"dns: Added ip [2-%"INT32"] %s to depth %"INT32" for %s.",
ds->m_numDnsIps[depth],
iptoa(ip),(int32_t)depth,ds->m_hostname);
}
}
// disregard any g_errnos cuz we will try again
g_errno = 0;
// just return if this blocks
if ( ! g_dns.sendToNextDNS ( ds , 20 ) ) {
log(LOG_DEBUG, "dns: sendToNextDns blocking for '%s'",
ds->m_hostname);
return ;
}
// if that does not block, then we are done... we got the final ip
// or g_errno is set. so call the callbacks.
log(LOG_DEBUG, "dns: getIpOfDNSWrapper calling returnIp for '%s'",
ds->m_hostname);
returnIp ( ds , ip );
// . otherwise, we must call the callback
// . call the callback w/ state and ip if there is one
// . g_errno may be set
//if ( ds->m_callback ) ds->m_callback ( ds->m_state , ip );
// free our state holding structure
//if ( ds->m_freeit ) mfree ( ds , sizeof(DnsState) ,"Dns" );
}
// returns false if blocked, sets g_errno and returns true otherwise
bool Dns::sendToNextDNS ( DnsState *ds , int32_t timeout ) {
//log(LOG_DEBUG, "dns: sendToNextDNS depth %d", ds->m_depth);
// let's clear g_errno since caller may have set it in gotIp()
g_errno = 0;
// if we have been at this too long, give up
int32_t now = getTime(); // time(NULL);//getTimeLocal();
int32_t delta = now - ds->m_startTime;
// quick fix if the system clock was changed on us
if ( delta < 0 ) ds->m_startTime = now;
//if ( delta > 100 ) ds->m_startTime = now;
if ( delta > TIMEOUT_TOTAL ) {
log(LOG_DEBUG,"dns: Timing out the request for %s. Took over "
"%"INT32" seconds. delta=%"INT32". now=%"INT32".",
ds->m_hostname,(int32_t)TIMEOUT_TOTAL,delta,now);
if ( ds->m_errno ) g_errno = ds->m_errno;
else g_errno = EDNSTIMEDOUT;
return true;
}
// if we have no more room to add to tried array, we're done,
// we've tried to ask too many nameservers already
if ( ds->m_numTried >= MAX_TRIED_IPS ) {
log(LOG_INFO,"dns: Asked maximum number of name servers, "
"%"INT32", for %s. Timing out.",(int32_t)MAX_TRIED_IPS,
ds->m_hostname);
if ( ds->m_errno ) g_errno = ds->m_errno;
else g_errno = EDNSTIMEDOUT;
return true;
}
// get the current depth. if we exhaust all nameserver ips at this
// depth we may have to decrease it until we find some nameservers
// we haven't yet asked.
int32_t depth = ds->m_depth;
top:
log(LOG_DEBUG, "dns: at 'top' for '%s'", ds->m_hostname);
int32_t n = -1;
// how many ip do we have at this depth level? save this for
// comparing down below.
int32_t numDnsIps = ds->m_numDnsIps[depth];
// each DnsState has a list of ips of the nameservers to ask
// but which one we ask first depends on this hash
if ( ds->m_numDnsIps[depth] > 0 ) {
// easy var
int32_t num = ds->m_numDnsIps[depth];
// . pick the first candidate to send to
// . this should not always be zero because picking the groupId
// and hostId to send to is now in Dns::getResponsibleHost()
// and uses key.n1 exclusively
n = ds->m_hostnameKey.n0 % num;
// conenvience ptr
int32_t *ips = ds->m_dnsIps[depth];
// save
int32_t orign = n;
do {
if (!isTimedOut(ips[n]))
break;
// note it
log(LOG_DEBUG,
"dns: skipping ip %s - timed out",
iptoa(ips[n]));
// advance
if ( ++n >= num )
n = 0;
} while (n != orign);
}
// . save n for wrap check below, to make sure we do not re-ask him
// . this may be -1 if we did not have any dns ips to pick from
int32_t startn = n;
// is the nth ip the next best candidate to send the request to?
checkip:
// get the nth ip
int32_t ip = 0;
if ( n >= 0 ) ip = ds->m_dnsIps[depth][n];
// loop over all the ips of nameservers we've already tried and make
// sure this one is not one of them. only check if n is valid (>=0)
bool tried = false;
for ( int32_t i = 0 ; n >=0 && i < ds->m_numTried ; i++ ) {
// check next tried ip if this one does not match.
if ( ip != ds->m_triedIps[i] ) continue;
// we've already tried this ip, do not send to it again
tried = true;
break;
}
// advance n if we already tried its ip, or if its ip is bogus.
// only do this if n >= 0 already, though. if it is -1 that means we
// have no candidates at this depth level
if ( n >= 0 && (tried || ip == 0 || ip == -1) ) {
// advance n
if ( ++n == ds->m_numDnsIps[depth] ) n = 0;
// if still a bogus ip, keep advancing
// but if we wrap, there are no valid n's
if ( n != startn ) goto checkip;
// set n to -1 to indicate no new and good ip available at
// this depth level
n = -1;
}
// if no ips to try, try the canonical names if there are some
if ( n == -1 && ds->m_numDnsNames[depth] > 0 ) {
// . return false if this blocked
// . this will remove the names from m_numDnsNames and
// put them in as ips into m_dnsIps.
// . it will decrease m_numDnsNames
// . this returns true if it does not block
if ( ! getIpOfDNS ( ds ) ) {
log(LOG_DEBUG, "dns: SendToNextDns blocked on "
"getIpOfDNS for '%s'", ds->m_hostname);
return false;
}
// getIpOfDNS may have set g_errno. it, as of this writing,
// only does that if we have too many ips already,
// MAX_DNS_IPS, so in that case, just ignore it and go down a
// level, it will not have added a new ip.
// NOTE: it will also set to EBADENGINEER if it caught
// a circular dependency. (see above)
g_errno = 0;
// ok, did we gain a new ip to try? if so, try run it through
// from the top.
if ( ds->m_numDnsIps[depth] > numDnsIps ) {
log(LOG_DEBUG, "dns: "
"SendToNextDNS going back to top 0 "
"for '%s'", ds->m_hostname);
goto top;
}
// if you made it here, we did not gain a new ip, probably
// because of error. n is still -1 to indicate no candidate
// at this depth level.
}
// ok, if we have no dns ips or hostnames to try at this point on
// this depth level then go back up to the previous level and see if
// those nameservers can recommend another set of nameservers to try.
// but this will be -1 if there are no more left to ask, and we will
// send back a EDNSTIMEDOUT error above.
if ( n == -1 ) {
depth--;
// decrease the depth, this may be the end of the chain... and
// we do not want to chain through all the root servers at depth 0
// because they are almost never wrong i guess.
if ( depth <= 0 ) {
log(LOG_DEBUG,"dns: Exhausted all chains except "
"root. Giving up for %s",ds->m_hostname);
if ( ds->m_errno ) g_errno = ds->m_errno;
else g_errno = EDNSTIMEDOUT;
return true;
}