//
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// OSSHttpdns.m
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// AliyunOSSiOS
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//
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// Created by zhouzhuo on 5/1/16.
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// Copyright © 2016 zhouzhuo. All rights reserved.
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//
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#import "OSSLog.h"
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#import "OSSHttpdns.h"
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#import "OSSIPv6Adapter.h"
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NSString * const OSS_HTTPDNS_SERVER_IP = @"203.107.1.1";
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NSString * const OSS_HTTPDNS_SERVER_PORT = @"80";
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NSString * const ACCOUNT_ID = @"181345";
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NSTimeInterval const MAX_ENDURABLE_EXPIRED_TIME_IN_SECOND = 60; // The DNS entry's expiration time in seconds. After it expires, the entry is invalid.
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NSTimeInterval const PRERESOLVE_IN_ADVANCE_IN_SECOND = 10; // Once the remaining valid time of an DNS entry is less than this number, issue a DNS request to prefetch the data.
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@interface IpObject : NSObject
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@property (nonatomic, copy) NSString * ip;
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@property (nonatomic, assign) NSTimeInterval expiredTime;
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@end
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@implementation IpObject
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@end
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@implementation OSSHttpdns {
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NSMutableDictionary * gHostIpMap;
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NSMutableSet * penddingSet;
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}
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+ (instancetype)sharedInstance {
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static OSSHttpdns * sharedInstance = nil;
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static dispatch_once_t onceToken;
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dispatch_once(&onceToken, ^{
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sharedInstance = [OSSHttpdns new];
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});
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return sharedInstance;
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}
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- (instancetype)init {
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if (self = [super init]) {
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gHostIpMap = [NSMutableDictionary new];
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penddingSet = [NSMutableSet new];
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}
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return self;
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}
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/**
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* OSS SDK specific
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*
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* @param host it needs strictly follow the domain's format, such as oss-cn-hangzhou.aliyuncs.com
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*
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* @return an ip in the ip list of the resolved host.
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*/
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- (NSString *)asynGetIpByHost:(NSString *)host {
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IpObject * ipObject = [gHostIpMap objectForKey:host];
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if (!ipObject) {
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// if the host is not resolved, asynchronously resolve it and return nil
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[self resolveHost:host];
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return nil;
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} else if ([[NSDate date] timeIntervalSince1970] - ipObject.expiredTime > MAX_ENDURABLE_EXPIRED_TIME_IN_SECOND) {
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// If the entry is expired, asynchronously resolve it and return nil.
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[self resolveHost:host];
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return nil;
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} else if (ipObject.expiredTime -[[NSDate date] timeIntervalSince1970] < PRERESOLVE_IN_ADVANCE_IN_SECOND) {
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// If the entry is about to expire, asynchronously resolve it and return the current value.
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[self resolveHost:host];
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return ipObject.ip;
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} else {
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// returns the current result.
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return ipObject.ip;
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}
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}
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/**
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* resolve the host asynchronously
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* If the host is being resolved, the call will be skipped.
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*
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* @param host the host to resolve
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*/
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- (void)resolveHost:(NSString *)host {
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@synchronized (self) {
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if ([penddingSet containsObject:host]) {
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return;
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} else {
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[penddingSet addObject:host];
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}
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}
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NSURL * url = [NSURL URLWithString:[NSString stringWithFormat:@"https://%@/%@/d?host=%@", [[OSSIPv6Adapter getInstance] handleIpv4Address:OSS_HTTPDNS_SERVER_IP], ACCOUNT_ID, host]];
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NSURLSession * session = [NSURLSession sharedSession];
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NSURLSessionDataTask * dataTask = [session dataTaskWithURL:url completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
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IpObject * ipObject = nil;
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NSUInteger statusCode = ((NSHTTPURLResponse *)response).statusCode;
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if (statusCode != 200) {
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OSSLogError(@"Httpdns resolve host: %@ failed, responseCode: %lu", host, (unsigned long)statusCode);
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} else {
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NSError *error = nil;
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NSDictionary *json = nil;
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if (data != nil){
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json = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
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}
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if (error != nil || json == nil){
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return;
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}
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NSTimeInterval expiredTime = [[NSDate new] timeIntervalSince1970] + [[json objectForKey:@"ttl"] longLongValue];
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NSArray *ips = [json objectForKey:@"ips"];
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if (ips == nil || [ips count] == 0) {
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OSSLogError(@"Httpdns resolve host: %@ failed, ip list empty.", host);
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} else {
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NSString * ip = ips[0];
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ipObject = [IpObject new];
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ipObject.expiredTime = expiredTime;
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ipObject.ip = ip;
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OSSLogDebug(@"Httpdns resolve host: %@ success, ip: %@, expiredTime: %lf", host, ipObject.ip, ipObject.expiredTime);
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}
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}
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@synchronized (self) {
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if (ipObject) {
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gHostIpMap[host] = ipObject;
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}
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[penddingSet removeObject:host];
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}
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}];
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[dataTask resume];
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}
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@end
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