299 lines
12 KiB
Mathematica
299 lines
12 KiB
Mathematica
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// MLDNSLookup.m
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// Monal
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//
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// Created by Anurodh Pokharel on 12/4/18.
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// Copyright © 2018 Monal.im. All rights reserved.
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//
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#import <stdint.h>
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#import "MLConstants.h"
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#import "MLDNSLookup.h"
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#import "HelperTools.h"
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@import Darwin.POSIX.sys.time;
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@interface MLDNSLookup()
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@end
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static NSMutableDictionary* _RRCache;
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@implementation MLDNSLookup
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+(void) initialize
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{
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_RRCache = [NSMutableDictionary new];
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}
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-(id) init
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{
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self = [super init];
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self.discoveredServers = [NSMutableArray new];
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return self;
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}
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-(void) doDiscoveryWithSecure:(BOOL) secure andDomain:(NSString*) domain withTimeout:(NSTimeInterval) query_timeout
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{
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DNSServiceRef sdRef;
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DNSServiceErrorType res;
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NSTimeInterval remainingTime = query_timeout;
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NSDate* startTime = [NSDate date];
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NSDictionary* context = @{
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@"isSecure": secure ? @YES : @NO,
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@"caller": self,
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};
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NSString* serviceDiscoveryString = [NSString stringWithFormat:@"_xmpp%@-client._tcp.%@", secure ? @"s" : @"", domain];
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res = DNSServiceQueryRecord(
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&sdRef,
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kDNSServiceFlagsReturnIntermediates, // | kDNSServiceFlagsValidate,
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0,
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[serviceDiscoveryString UTF8String],
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kDNSServiceType_SRV,
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kDNSServiceClass_IN,
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query_cb,
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(__bridge void*)(context)
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);
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if(res == kDNSServiceErr_NoError)
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{
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int sock = DNSServiceRefSockFD(sdRef);
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while (remainingTime > 0)
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{
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fd_set set;
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FD_ZERO(&set);
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FD_SET(sock, &set);
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struct timeval tv;
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tv.tv_sec = (time_t)remainingTime;
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tv.tv_usec = (int32_t)((remainingTime - tv.tv_sec) * 1000000);
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int result = select(FD_SETSIZE, &set, NULL, NULL, &tv);
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DDLogVerbose(@"DNS select() returned %d", result);
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if(result == 1)
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{
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if(FD_ISSET(sock, &set))
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{
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res = DNSServiceProcessResult(sdRef);
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if(res != kDNSServiceErr_NoError)
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DDLogError(@"Error %d reading the DNS SRV records for: %@", res, serviceDiscoveryString);
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break;
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}
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}
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else if(result == 0)
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{
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DDLogError(@"DNS SRV select() timed out for: %@", serviceDiscoveryString);
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break;
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}
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else
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{
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if(errno == EINTR)
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{
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DDLogInfo(@"DNS SRV select() interrupted, retry for: %@", serviceDiscoveryString);
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}
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else
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{
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DDLogError(@"DNS SRV select() returned %d errno %d %s for %@", result, errno, strerror(errno), serviceDiscoveryString);
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break;
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}
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}
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NSTimeInterval elapsed = [[NSDate date] timeIntervalSinceDate:startTime];
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remainingTime -= elapsed;
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}
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DNSServiceRefDeallocate(sdRef);
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}
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else
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DDLogError(@"DNS SRV query returned error %d for: %@", res, serviceDiscoveryString);
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}
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-(NSArray*) doRealDnsDiscoverOnDomain:(NSString*) domain withTimeout:(NSTimeInterval) timeout
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{
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//the whole function is blocking, this synchronized block makes sure we resolve one query at a time (scoped to this class instance)
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@synchronized(self) {
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@synchronized(self.discoveredServers) {
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[self.discoveredServers removeAllObjects];
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}
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//request xmpps and xmpp records, xmpps will be preferred (use a dispatch queue to fetch xmpp and xmpps concurrently)
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DDLogVerbose(@"Querying DNS for xmpps AND xmpp records...");
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dispatch_queue_t queue = dispatch_queue_create("im.monal.dnsqueue", DISPATCH_QUEUE_CONCURRENT);
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dispatch_async(queue, ^{
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[self doDiscoveryWithSecure:YES andDomain:domain withTimeout:timeout];
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});
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dispatch_async(queue, ^{
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[self doDiscoveryWithSecure:NO andDomain:domain withTimeout:timeout];
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});
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//wait for both dns queries to complete
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dispatch_barrier_sync(queue, ^{
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DDLogVerbose(@"SRV DNS queries completed (xmpps AND xmpp)...");
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// [HelperTools flushLogsWithTimeout:0.100];
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// exit(0);
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});
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@synchronized(self.discoveredServers) {
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//early return
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if([self.discoveredServers count] == 0)
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{
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DDLogInfo(@"No SRV records could be found, returning empty NSArray...");
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return @[];
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}
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//we ignore weights here for simplicity
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[self.discoveredServers sortUsingDescriptors:@[[[NSSortDescriptor alloc] initWithKey:@"priority" ascending:YES]]];
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//calculate lowest timeout
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u_int32_t lowest_ttl = UINT32_MAX;
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for(NSDictionary* entry in self.discoveredServers)
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{
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#ifdef DEBUG
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MLAssert([entry isKindOfClass:[NSDictionary class]], @"discoveredServers has an entry that is NOT of type NSDictionary", (@{
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@"entry": entry,
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@"discoveredServers": self.discoveredServers,
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}));
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#endif
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if([entry isKindOfClass:[NSDictionary class]])
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lowest_ttl = MIN(lowest_ttl, [entry[@"ttl"] unsignedIntValue]);
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}
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DDLogVerbose(@"Lowest ttl for SRV records: %u", lowest_ttl);
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//update resource record cache with discovered servers list
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DDLogVerbose(@"Updating RRCache with: %@", self.discoveredServers);
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@synchronized(_RRCache) {
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_RRCache[domain] = @{
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@"timeout": [NSDate dateWithTimeIntervalSinceNow:lowest_ttl],
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@"records": [self.discoveredServers copy],
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};
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}
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//return discovered servers list
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return [self.discoveredServers copy];
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}
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}
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}
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-(NSArray*) dnsDiscoverOnDomain:(NSString*) domain
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{
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/*
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@synchronized(_RRCache) {
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if(_RRCache[domain] != nil && [_RRCache[domain][@"timeout"] timeIntervalSinceNow] > 0)
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{
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//update our cache in background
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dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
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[self doRealDnsDiscoverOnDomain:domain withTimeout:16ul]; //long query timeout (this is a background query)
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});
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return [_RRCache[domain][@"records"] copy];
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}
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}
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*/
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return [self doRealDnsDiscoverOnDomain:domain withTimeout:8ul]; //short query timeout (we are waiting for this query)
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}
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// ********************************************** C code below **********************************************
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char* ConvertDomainLabelToCString_withescape(const domainLabel* label, char* ptr, char esc)
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{
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const u_char * src = label->c; // Domain label we're reading
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const u_char len = *src++; // Read length of this (non-null) label
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const u_char *const end = src + len; // Work out where the label ends
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if (len > MAX_DOMAIN_LABEL) return(NULL); // If illegal label, abort
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while (src < end) // While we have characters in the label
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{
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u_char c = *src++;
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if (esc)
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{
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if (c == '.') // If character is a dot,
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*ptr++ = esc; // Output escape character
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else if (c <= ' ') // If non-printing ascii,
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{ // Output decimal escape sequence
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*ptr++ = esc;
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*ptr++ = (char) ('0' + (c / 100) );
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*ptr++ = (char) ('0' + (c / 10) % 10);
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c = (u_char)('0' + (c ) % 10);
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}
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}
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*ptr++ = (char)c; // Copy the character
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}
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*ptr = 0; // Null-terminate the string
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return(ptr); // and return
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}
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char* ConvertDomainNameToCString_withescape(const domainName* name, int len, char* ptr, char esc)
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{
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const u_char *src = name->c; // Domain name we're reading
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const u_char *const max = name->c + MIN(MAX_DOMAIN_NAME, len); // Maximum that's valid
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if (*src == 0) *ptr++ = '.'; // Special case: For root, just write a dot
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while (*src) // While more characters in the domain name
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{
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if (src + 1 + *src >= max) return(NULL);
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ptr = ConvertDomainLabelToCString_withescape((const domainLabel *)src, ptr, esc);
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if (!ptr) return(NULL);
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src += 1 + *src;
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*ptr++ = '.'; // Write the dot after the label
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}
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*ptr++ = 0; // Null-terminate the string
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return(ptr); // and return
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}
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void query_cb(const DNSServiceRef DNSServiceRef, const DNSServiceFlags flags, const u_int32_t interfaceIndex, const DNSServiceErrorType errorCode, const char* name __unused, const u_int16_t rrtype, const u_int16_t rrclass, const u_int16_t rdlen, const void* rdata, const u_int32_t ttl, void* _context)
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{
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//make sure the compiler doesn't cry because of unused arguments
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(void)DNSServiceRef;
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(void)interfaceIndex;
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(void)rrclass;
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//just ignore errors (don't fill anything into the discoveredServers array)
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if(errorCode)
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{
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DDLogVerbose(@"query callback: error==%d\n", errorCode);
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return;
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}
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NSDictionary* context = (__bridge NSDictionary*)_context;
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BOOL isSecure = [context[@"isSecure"] boolValue];
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MLDNSLookup* caller = (MLDNSLookup*)context[@"caller"];
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if(rrtype == T_SRV)
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{
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srv_rdata* srv = (srv_rdata*)rdata;
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char targetStr[MAX_CSTRING];
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int srvDomainLen = rdlen - sizeof(srv->priority) - sizeof(srv->weight) - sizeof(srv->port);
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if(srvDomainLen > MAX_DOMAIN_NAME)
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return;
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ConvertDomainNameToCString_withescape(&srv->target, srvDomainLen, targetStr, 0);
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DDLogVerbose(@"pri=%d, w=%d, port=%d, target=%s, ttl=%u, flags=%u\n", ntohs(srv->priority), ntohs(srv->weight), ntohs(srv->port), targetStr, ttl, (u_int32_t)flags);
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NSString* theServer = [NSString stringWithUTF8String:targetStr];
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NSNumber* prio = [NSNumber numberWithUnsignedInt:(ntohs(srv->priority) + (isSecure == YES ? 0 : UINT16_MAX))]; // prefer TLS over STARTTLS
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NSNumber* weight = [NSNumber numberWithInt:ntohs(srv->weight)];
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NSNumber* thePort = [NSNumber numberWithInt:ntohs(srv->port)];
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if(theServer && prio && weight && thePort) {
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// Check if service is not provided (ignored for xmpps records, NOT ignored for xmpp records)
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bool serviceEnabled = ![theServer isEqualToString:@"."];
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if(serviceEnabled == false && isSecure == YES)
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return;
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// Validate that the domain ends with at dot (and ignore this entry, if not)
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if([theServer hasSuffix:@"."] == NO)
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return;
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//add result to discovered severs list
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@synchronized(caller.discoveredServers) {
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[caller.discoveredServers addObject:@{
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@"priority": prio,
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@"server": theServer,
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@"port": thePort,
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@"isSecure": [NSNumber numberWithBool:isSecure],
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@"weight": weight,
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@"isEnabled": [NSNumber numberWithBool:serviceEnabled],
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@"ttl": [NSNumber numberWithUnsignedInt:ttl],
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}];
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}
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}
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}
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}
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@end
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