Use getaddrinfo() instead of gethostbyname().

The latter is not re-entrant, so not thread-safe.

At the same time, support round-robin DNS in a sort of trivial way.

net/http_client.cpp

@@ -26,11 +26,13 @@
 namespace net {
 
 Connection::Connection() 
-		: port_(-1), sock_(-1) {
+		: port_(-1), sock_(-1), resolved_(NULL) {
 }
 
 Connection::~Connection() {
 	Disconnect();
+	if (resolved_ != NULL)
+		DNSResolveFree(resolved_);
 }
 
 // For whatever crazy reason, htons isn't available on android x86 on the build server. so here we go.
@@ -45,21 +47,17 @@ bool Connection::Resolve(const char *host, int port) {
 	host_ = host;
 	port_ = port;
 
-	const char *err;
-	const char *ip = net::DNSResolveTry(host, &err);
-	if (ip == NULL) {
-		ELOG("Failed to resolve host %s", host);
+	char port_str[10];
+	snprintf(port_str, sizeof(port_str), "%d", port);
+	
+	std::string err;
+	if (!net::DNSResolve(host, port_str, &resolved_, err)) {
+		ELOG("Failed to resolve host %s: %s", host, err.c_str());
 		// So that future calls fail.
 		port_ = 0;
 		return false;
 	}
-	// VLOG(1) << "Resolved " << host << " to " << ip;
-	remote_.sin_family = AF_INET;
-	int tmpres = net::inet_pton(AF_INET, ip, (void *)(&(remote_.sin_addr.s_addr)));
-	CHECK_GE(tmpres, 0);	// << "inet_pton failed";
-	CHECK_NE(0, tmpres);	// << ip << " not a valid IP address";
-	remote_.sin_port = myhtons(port);
-	free((void *)ip);
+
 	return true;
 }
 
@@ -68,11 +66,16 @@ void Connection::Connect() {
 	sock_ = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
 	CHECK_GE(sock_, 0);
 
-	// poll once per second.. should find a way to do this blocking.
-	int retval = -1;
-	while (retval < 0) {
-		retval = connect(sock_, (sockaddr *)&remote_, sizeof(struct sockaddr));
-		if (retval >= 0) break;
+	for (int tries = 100; tries > 0; --tries) {
+		for (addrinfo *possible = resolved_; possible != NULL; possible = possible->ai_next) {
+			// TODO: Could support ipv6 without huge difficulty...
+			if (possible->ai_family != AF_INET)
+				continue;
+
+			int retval = connect(sock_, possible->ai_addr, (int)possible->ai_addrlen);
+			if (retval >= 0)
+				return;
+		}
 #ifdef _WIN32
 		Sleep(1);
 #else

net/http_client.h

@@ -16,6 +16,7 @@
 #include <arpa/inet.h>
 #endif
 #include <sys/socket.h>
+#include <netdb.h>
 #endif
 
 namespace net {
@@ -43,7 +44,7 @@ protected:
 	std::string host_;
 	int port_;
 
-	sockaddr_in remote_;
+	addrinfo *resolved_;
 
 private:
 	uintptr_t sock_;

net/resolve.cpp

@@ -1,13 +1,15 @@
-	#include "net/resolve.h"
+#include "net/resolve.h"
+#include "base/logging.h"
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <string>
 
 
 #ifndef _WIN32
 #include <arpa/inet.h>
-#include <netdb.h>	// gethostbyname
+#include <netdb.h>
 #include <sys/socket.h>
 #else
 #include <WinSock2.h>
@@ -69,6 +71,46 @@ char *DNSResolve(const char *host)
 	return ip;
 }
 
+bool DNSResolve(const std::string &host, const std::string &service, addrinfo **res, std::string &error)
+{
+	addrinfo hints = {0};
+	// TODO: Might be uses to lookup other values.
+	hints.ai_socktype = SOCK_STREAM;
+	hints.ai_flags = AI_V4MAPPED | AI_ADDRCONFIG;
+	hints.ai_protocol = IPPROTO_TCP;
+
+	const char *servicep = service.length() == 0 ? NULL : service.c_str();
+
+	*res = NULL;
+	int result = getaddrinfo(host.c_str(), servicep, &hints, res);
+	if (result == EAI_AGAIN)
+	{
+		// Temporary failure.  Since this already blocks, let's just try once more.
+#ifdef _WIN32
+		Sleep(1);
+#else
+		sleep(1);
+#endif
+		result = getaddrinfo(host.c_str(), servicep, &hints, res);
+	}
+
+	if (result != 0)
+	{
+		error = gai_strerror(result);
+		if (*res != NULL)
+			freeaddrinfo(*res);
+		*res = NULL;
+		return false;
+	}
+
+	return true;
+}
+
+void DNSResolveFree(addrinfo *res)
+{
+	freeaddrinfo(res);
+}
+
 int inet_pton(int af, const char* src, void* dst)
 {
 	if (af == AF_INET)

net/resolve.h

@@ -1,5 +1,8 @@
-#ifndef _NET_RESOLVE_H
-#define _NET_RESOLVE_H
+#pragma once
+
+#include <string>
+
+struct addrinfo;
 
 namespace net {
 
@@ -11,6 +14,8 @@ void Shutdown();
 char *DNSResolveTry(const char *host, const char **err);
 char *DNSResolve(const char *host);
 
+bool DNSResolve(const std::string &host, const std::string &service, addrinfo **res, std::string &error);
+void DNSResolveFree(addrinfo *res);
+
 int inet_pton(int af, const char* src, void* dst);
 }  // namespace net
-#endif