improved ip assignment

more stable error handling

client.cpp

@@ -31,11 +31,14 @@ using namespace std;
 
 const Worker::TunnelHeader::Magic Client::magic("hanc");
 
-Client::Client(int tunnelMtu, const char *deviceName, uint32_t serverIp, int maxPolls,
+Client::Client(int tunnelMtu, const char *deviceName, uint32_t serverIp,
-			   const char *passphrase, uid_t uid, gid_t gid, bool changeEchoId, bool changeEchoSeq)
+               int maxPolls, const char *passphrase, uid_t uid, gid_t gid,
+               bool changeEchoId, bool changeEchoSeq, uint32_t desiredIp)
 : Worker(tunnelMtu, deviceName, false, uid, gid), auth(passphrase)
 {
 	this->serverIp = serverIp;
+    this->clientIp = INADDR_NONE;
+    this->desiredIp = desiredIp;
 	this->maxPolls = maxPolls;
 	this->nextEchoId = Utility::rand();
 	this->changeEchoId = changeEchoId;
@@ -54,6 +57,7 @@ void Client::sendConnectionRequest()
 {
 	Server::ClientConnectData *connectData = (Server::ClientConnectData *)echoSendPayloadBuffer();
 	connectData->maxPolls = maxPolls;
+    connectData->desiredIp = desiredIp;
 
 	syslog(LOG_DEBUG, "sending connection request");
 
@@ -97,9 +101,6 @@ bool Client::handleEchoData(const TunnelHeader &header, int dataLength, uint32_t
 		case TunnelHeader::TYPE_RESET_CONNECTION:
 			syslog(LOG_DEBUG, "reset reveiced");
 
-			if (privilegesDropped)
-				throw Exception("cannot reconnect without root privileges");
-
 			sendConnectionRequest();
 			return true;
 		case TunnelHeader::TYPE_SERVER_FULL:
@@ -128,7 +129,15 @@ bool Client::handleEchoData(const TunnelHeader &header, int dataLength, uint32_t
 				syslog(LOG_INFO, "connection established");
 
 				uint32_t ip = ntohl(*(uint32_t *)echoReceivePayloadBuffer());
+                if (ip != clientIp)
+				{
+                    if (privilegesDropped)
+                        throw Exception("could not get the same ip address, so root privileges are required to change it");
+
+                    clientIp = ip;
+                    desiredIp = ip;
                     tun->setIp(ip, (ip & 0xffffff00) + 1, false);
+                }
 				state = STATE_ESTABLISHED;
 
 				dropPrivileges();

client.h

@@ -28,8 +28,9 @@
 class Client : public Worker
 {
 public:
-	Client(int tunnelMtu, const char *deviceName, uint32_t serverIp, int maxPolls,
+	Client(int tunnelMtu, const char *deviceName, uint32_t serverIp,
-		   const char *passphrase, uid_t uid, gid_t gid, bool changeEchoId, bool changeEchoSeq);
+           int maxPolls, const char *passphrase, uid_t uid, gid_t gid,
+           bool changeEchoId, bool changeEchoSeq, uint32_t desiredIp);
 	virtual ~Client();
 
 	virtual void run();
@@ -59,6 +60,8 @@ protected:
 	Auth auth;
 
 	uint32_t serverIp;
+    uint32_t clientIp;
+    uint32_t desiredIp;
 
 	int maxPolls;
 	int pollTimeoutNr;

echo.cpp

@@ -26,6 +26,9 @@
 #include <netinet/ip.h>
 #include <arpa/inet.h>
 #include <unistd.h>
+#include <errno.h>
+#include <syslog.h>
+#include <string.h>
 
 typedef ip IpHeader;
 
@@ -72,7 +75,7 @@ void Echo::send(int payloadLength, uint32_t realIp, bool reply, uint16_t id, uin
 
 	int result = sendto(fd, sendBuffer + sizeof(IpHeader), payloadLength + sizeof(EchoHeader), 0, (struct sockaddr *)&target, sizeof(struct sockaddr_in));
 	if (result == -1)
-		throw Exception("sendto", true);
+        syslog(LOG_ERR, "error sending icmp packet: %s", strerror(errno));
 }
 
 int Echo::receive(uint32_t &realIp, bool &reply, uint16_t &id, uint16_t &seq)
@@ -82,7 +85,10 @@ int Echo::receive(uint32_t &realIp, bool &reply, uint16_t &id, uint16_t &seq)
 
 	int dataLength = recvfrom(fd, receiveBuffer, bufferSize, 0, (struct sockaddr *)&source, (socklen_t *)&source_addr_len);
 	if (dataLength == -1)
-		throw Exception("recvfrom", true);
+    {
+        syslog(LOG_ERR, "error receiving icmp packet: %s", strerror(errno));
+        return -1;
+    }
 
 	if (dataLength < sizeof(IpHeader) + sizeof(EchoHeader))
 		return -1;

main.cpp

@@ -36,7 +36,7 @@ void usage()
 	printf(
 		"Hans - IP over ICMP version 0.3.1\n\n"
 		"RUN AS SERVER\n"
-		"  hans -s network [-fvr] [-p password] [-u unprivileged_user] [-d tun_device] [-m reference_mtu]\n\n"
+		"  hans -s network [-fvr] [-p password] [-u unprivileged_user] [-d tun_device] [-m reference_mtu] [-a ip]\n\n"
 		"RUN AS CLIENT\n"
 		"  hans -c server  [-fv]  [-p password] [-u unprivileged_user] [-d tun_device] [-m reference_mtu] [-w polls]\n\n"
 		"ARGUMENTS\n"
@@ -55,6 +55,7 @@ void usage()
 		"                0 disables polling. Defaults to 10.\n"
 		"  -i            Change the echo id for every echo request.\n"
         "  -q            Change the echo sequence number for every echo request.\n"
+        "  -a ip         Try to get assigned the given tunnel ip address.\n"
 	);
 }
 
@@ -70,6 +71,7 @@ int main(int argc, char *argv[])
 	int mtu = 1500;
 	int maxPolls = 10;
 	uint32_t network = INADDR_NONE;
+    uint32_t clientIp = INADDR_NONE;
 	bool answerPing = false;
 	uid_t uid = 0;
 	gid_t gid = 0;
@@ -80,7 +82,7 @@ int main(int argc, char *argv[])
 	openlog(argv[0], LOG_PERROR, LOG_DAEMON);
 
 	int c;
-	while ((c = getopt(argc, argv, "fru:d:p:s:c:m:w:qiv")) != -1)
+	while ((c = getopt(argc, argv, "fru:d:p:s:c:m:w:qiva:")) != -1)
 	{
 		switch(c) {
 			case 'f':
@@ -124,6 +126,9 @@ int main(int argc, char *argv[])
 			case 'v':
 				verbose = true;
 				break;
+			case 'a':
+				clientIp = ntohl(inet_addr(optarg));
+				break;
 			default:
 				usage();
 				return 1;
@@ -190,7 +195,7 @@ int main(int argc, char *argv[])
 				serverIp = *(uint32_t *)he->h_addr;
 			}
 
-			worker = new Client(mtu, device, ntohl(serverIp), maxPolls, password, uid, gid, changeEchoId, changeEchoSeq);
+			worker = new Client(mtu, device, ntohl(serverIp), maxPolls, password, uid, gid, changeEchoId, changeEchoSeq, clientIp);
 		}
 
 		if (!foreground)

server.cpp

@@ -28,6 +28,8 @@
 
 using namespace std;
 
+#define FIRST_ASSIGNED_IP_OFFSET 100
+
 const Worker::TunnelHeader::Magic Server::magic("hans");
 
 Server::Server(int tunnelMtu, const char *deviceName, const char *passphrase, uint32_t network, bool answerEcho, uid_t uid, gid_t gid, int pollTimeout)
@@ -35,6 +37,7 @@ Server::Server(int tunnelMtu, const char *deviceName, const char *passphrase, ui
 {
 	this->network = network & 0xffffff00;
 	this->pollTimeout = pollTimeout;
+    this->latestAssignedIpOffset = FIRST_ASSIGNED_IP_OFFSET - 1;
 
 	tun->setIp(this->network + 1, this->network + 2, true);
 
@@ -65,7 +68,7 @@ void Server::handleUnknownClient(const TunnelHeader &header, int dataLength, uin
 
 	client.maxPolls = connectData->maxPolls;
 	client.state = ClientData::STATE_NEW;
-	client.tunnelIp = reserveTunnelIp();
+	client.tunnelIp = reserveTunnelIp(connectData->desiredIp);
 
 	syslog(LOG_DEBUG, "new client: %s (%s)\n", Utility::formatIp(client.realIp).c_str(), Utility::formatIp(client.tunnelIp).c_str());
 
@@ -186,7 +189,6 @@ bool Server::handleEchoData(const TunnelHeader &header, int dataLength, uint32_t
 				if (dataLength == 0)
 				{
 					syslog(LOG_WARNING, "received empty data packet");
-					throw 0;
 					return true;
 				}
 
@@ -294,7 +296,7 @@ void Server::sendEchoToClient(ClientData *client, int type, int dataLength)
 
 void Server::releaseTunnelIp(uint32_t tunnelIp)
 {
-	usedIps.remove(tunnelIp);
+	usedIps.erase(tunnelIp);
 }
 
 void Server::handleTimeout()
@@ -314,23 +316,34 @@ void Server::handleTimeout()
 	setTimeout(KEEP_ALIVE_INTERVAL);
 }
 
-uint32_t Server::reserveTunnelIp()
+uint32_t Server::reserveTunnelIp(uint32_t desiredIp)
 {
-	uint32_t ip = network + 2;
+    if (desiredIp > network + 1 && desiredIp < network + 255 && !usedIps.count(desiredIp))
-
-	list<uint32_t>::iterator i;
-	for (i = usedIps.begin(); i != usedIps.end(); ++i)
     {
-		if (*i > ip)
+        usedIps.insert(desiredIp);
-			break;
+        return desiredIp;
-		ip = ip + 1;
     }
 
-	if (ip - network >= 255)
+    bool ipAvailable = false;
+
+    for (int i = 0; i < 255 - FIRST_ASSIGNED_IP_OFFSET; i++)
+    {
+        latestAssignedIpOffset++;
+        if (latestAssignedIpOffset == 255)
+            latestAssignedIpOffset = FIRST_ASSIGNED_IP_OFFSET;
+
+        if (!usedIps.count(network + latestAssignedIpOffset))
+        {
+            ipAvailable = true;
+            break;
+        }
+    }
+
+	if (!ipAvailable)
 		return 0;
 
-	usedIps.insert(i, ip);
+	usedIps.insert(network + latestAssignedIpOffset);
-	return ip;
+	return network + latestAssignedIpOffset;
 }
 
 void Server::run()

server.h

@@ -26,7 +26,7 @@
 #include <map>
 #include <queue>
 #include <vector>
-#include <list>
+#include <set>
 
 class Server : public Worker
 {
@@ -37,6 +37,7 @@ public:
 	struct ClientConnectData
 	{
 		uint8_t maxPolls;
+        uint32_t desiredIp;
 	};
 
 	static const Worker::TunnelHeader::Magic magic;
@@ -101,7 +102,7 @@ protected:
 
 	void pollReceived(ClientData *client, uint16_t echoId, uint16_t echoSeq);
 
-	uint32_t reserveTunnelIp();
+	uint32_t reserveTunnelIp(uint32_t desiredIp);
 	void releaseTunnelIp(uint32_t tunnelIp);
 
 	ClientData *getClientByTunnelIp(uint32_t ip);
@@ -110,7 +111,8 @@ protected:
 	Auth auth;
 
 	uint32_t network;
-	std::list<uint32_t> usedIps;
+	std::set<uint32_t> usedIps;
+    uint32_t latestAssignedIpOffset;
 
 	Time pollTimeout;
 

tun.cpp

@@ -89,21 +89,14 @@ void Tun::setIp(uint32_t ip, uint32_t destIp, bool includeSubnet)
 void Tun::write(const char *buffer, int length)
 {
 	if (tun_write(fd, (char *)buffer, length) == -1)
-	{
+		syslog(LOG_ERR, "error writing %d bytes to tun: %s", length, strerror(errno));
-		syslog(LOG_ERR, "error writing %d bytes to tun", length);
-		if (errno != EINVAL) // can be caused by invalid data packet
-			throw Exception("writing to tun", true);
-	}
 }
 
 int Tun::read(char *buffer)
 {
 	int length = tun_read(fd, buffer, mtu);
 	if (length == -1)
-	{
+		syslog(LOG_ERR, "error reading from tun: %s", strerror(errno));
-		syslog(LOG_ERR, "error reading from tun", length);
-		throw Exception("reading from tun", true);
-	}
 	return length;
 }
 

worker.cpp

@@ -175,6 +175,7 @@ void Worker::run()
 			if (dataLength == 0)
 				throw Exception("tunnel closed");
 
+            if (dataLength != -1)
                 handleTunData(dataLength, sourceIp, destIp);
 		}
 	}