I'm developing an application in C++ for Windows 7, that sets up a TFTP server to communicate to an embedded device. The device is supposed to be connected directly to the Ethernet port, and it expects a TFTP server on 192.168.1.19 static address.
To simplify user experience, I want the following scenario:
present a list of all network connections registered in the system to the user (same list as in "Control Panel\Network and Internet\Network Connections")
allow to choose one connection
memorize its IPv4 configuration
set IPv4 configuration to 192.168.1.19 and 255.255.255.0
after TFTP job done, restore original IPv4 configuration
The problem I encountered is a mix of the following:
when no Ethernet cable plugged, neither of GetAdaptersInfo, GetInterfaceInfo, GetAdaptersAddresses list the connection I'm interested in;
even if I get that connection, I'm not sure which API to use to set DHCP on/off, static IP, network mask.
I tried using netsh, and it works fine, but I don't want to run it from my app, because I don't want to deal with non-English characters in the connection names.
Suggestions welcome,
Thanks!
===== edit #1
Tried WMI query "Select * From Win32_NetworkAdapter Where NetConnectionID = 'Local Area Connection'" -- no IP address in the feedback, although I can see it in the Control Panel connection properties.
Queries involving Win32_NetworkConnection don't return anything at all.
I ended up using:
"Select * From Win32_NetworkAdapter Where PhysicalAdapter='True' AND AdapterTypeID=0" query to list adapters/connection names/guid - works pretty good
registry to read configuration via guid
netsh to do configuration via connection name. Yes, I had much fun with locales.
I frankly didn't find a more reliable way to work with disconnected connections. Hope this helps. If anyone has better solutions - I'd be glad to see them!
Related
I need to find out the address of the TFTP server that is specified in the DHCP configuration.
When the PC is started on, the computer receives the IP address via DHCP, then downloads the image from the PXE server. During the download of the distribution, I need to run a utility that accesses the Database to the server from which this image was downloaded (where the TFTP server is running).
In theory, it would be possible to register the necessary address of the TFTP server in the downloadable image of the distribution. But the bottom line is that such a scheme exists in various subnets. And specifying its TFTP server for each subnet is an irrational approach. It would be more convenient to get the address of the TFTP server from the DHCP server, which is listed there as next-server
I found something similar at Busybox.
Is it possible to implement something like this in C/C++ and how can it be done? I don't have any ideas.
Some example of the code of contacting the DHCP server to get an address or parameter. Open a socket and make a request or something like that... At least I haven't found any similar examples on the Internet.
P.S. I will put a dislike and send it to read man, than I will answer the question constructively. Nice!
If you are using the ISC dhcp-client then
man dhclient-script
If you are using some other dhcp client then it might have support for calling scripts too. Or it might store the dhcp lease somewhere in a parseable format, like /var/lib/dhcp/dhclient.leases. You can extract the dhcp options from that.
Now that apple has changed their review environment to an IPv6 only network ive been running into troubles with my application while testing.
The application requires the user to input their server/systems IP address, port (4401) and credentials to gain access to the application. Following the guidelines provided by apple i set up a NAT64 environment to test my application's compatibility. Running iOS 9.3.2 on an iphone 5s.
My work environment has several internal networks. I connected my iMac to the internal server (10.10.50.XX) via Ethernet which also has an external IP which is what i provide to apple. The 50 network does not run behind a proxy, but there are some sites which get filtered, but can access by confirming. I then shared my Ethernet connection through WiFI.
I connected the device and had internet access with the same pages being filtered. The device gets assigned a local-link address of 169.254.XX.XX. From what ive read my device is connecting to the ipv6 only network correctly, as the iphone does not show the ipv6 address only local link.
If I am correctly connected to the shared IPv6 network, the problem I am having is connecting to my server on the 50 network from my application. The application fails when ever i try to connected to the 10.10.50.XX network or the external(understandable because my imac is on the 50 internal network) .
Testing the application using IPv4 with a wireless router that is connected to the 50 network runs perfectly.I think it is an issue with the local link address not being able to see the 50 network or something.
Heres some brief background info on how i connect to the server. The user inputs all the credentials and the IP address and port of the server they want to connect to. The application saves this as a text (utf-8) and uses boost shared_ptr to send it to the cpp connection class which validates the credentials and provides access to the user. This cpp connection class handles the connection, synchronization, logging, requests and response from the server.
Is it possible to somehow get access to the 50 network, using the NAT64 internet sharing option?
If you're passing an IP address straight down to your network lib, then no. When your device is on the IPv6-only side of the NAT64, the server's IPv4 address is useless.
You almost certainly need a DNS name for the server you're trying to reach. The NAT64 relies first on DNS64 to create IPv6 addresses for your application when the server is IPv4-only. These synthesised addresses contain the IPv4 address(es) for the server, giving the NAT64 the information it needs to translate from IPv6 to IPv4.
Updating this to add: as suggested by user102008 in the comment thread attached to this answer, you may also be able to pass the IPv4 string literal though getaddrinfo() (see code listing 10-1 on this page). When you're behind a NAT64, a synthesised IPv6 address should be among the results returned by that call. The NAT64 will translate from this address back to IPv4 to reach the host you specified. In this case, if the system knows the correct prefix to use for the NAT64, a hostname is not necessary.
I am writing Win32 API (C++) code to query a network for certain information. One of those pieces of information is the DHCP lease end time. I was able to get most of the information I needed from the GetIpNetTable (and/or GetIpNetTable2) functions; but after loads of Google, MSDN, Stackoverflow searches I cannot find a way of getting all of the lease information from an arbitrary client (this code does not run on the server). I'm familiar with the GetAdaptersInfo function but that only retrieves information for the current machine, not all machines on the network. Does anyone know of a way to map out all of the DHCP lease information of a network from an arbitrary client?
You could do this by implementing a read-only DHCP server. The clients will send out a DHCPDISCOVER message as a broadcast (on UDP port 67) which you can receive. The responding DHCP server will broadcast back the DHCPOFFER including the client's MAC address, relevant IP information and the lease time. If the client accepts these settings it will now broadcast a DHCPREQUEST message so your read-only server will know the client will (try to) use the DHCPOFFER information. You can't see the DHPCACK acknowledge from the server but if things fail for the client it will send a new DHCPDISCOVER. This way you can build a table of DHCP information including lease times for local clients.
I need to write a win32 c/c++ application which will be able to determine whether the PC it's running on is connected to one of 2 networks. The first network is the company LAN (which has no internet connection) and the second network is a standalone switch with a single PC connected to it (the PC that the program is running on).
I'm pretty new to network programming but so far I have tried testing to see if a network drive which is held on our LAN can be mapped. This works fine if the PC is connected to the LAN, the drive mapping succeeds so so LAN detection is successful. However, if the PC is connected to the switch, this results in a VERY long timeout which is not a suitable as it will delay the program so much as to make it unusable.
Does anyone have any alternative suggestions?
I'm using c/c++ in VS 6.0
[Update]
Whilst trying a few different ideas and looking at some of the suggestions below I thought I should update with some additional information as many (if not all) of the suggestions I don't think will work.
(1) The aforementioned LAN has no external connections at all, it is completely isolated so no resolving of external DNS or pinging websites is possible.
(2) Hostname, MAC address, IP, Default Gateway, Subnet etc etc (basically everything you see in ipconfig -all) are all manually configured (not dynamic from the router) so checking any of these settings will return the same whether connected to the LAN or the switch.
(3) Due to point (2), any attempts to communicate with the switch seem to be unsuccessful, in fact almost all networking commands (ping, arp etc) seem to fail - I think due to the machine trying to connect to the LAN when it isn't there :-(
One thing I have found which works is pinging the default gateway IP which times out when connected to the switch. This is sort of ok as I can reduce the timeout of ping so it doesn't just hang for ages but it feels like a bit of a hack and I would certainly appreciate any better solutions.
Thanks
As far as TCP/IP is concerned there is no such thing as a LAN on WAN. There are a set of non-internet routable addresses like 192.168.x.x and 10.x.x.x but these are sometimes used by ISP short of IP addresses.
You best bet is to use Asynchronous APIs when making TCP/IP connections. WIN32 defines a whole buch of OVERLAPPED APIs for this purpose. This will prevent your application from grinding to a halt while waiting for a remote connection.
Alternatively put the socket stuff into another thread and then only notify the UI when the operation is done.
I would first try to differentiate between the two using information available locally--that is, from your computer. Does the output of ipconfig /all differ depending on which network you're connected to? If so, exploit that difference if you can.
Is it possible to get the MAC address of the standalone switch? Of the switch that controls the company LAN? That would be a sure way to tell. Unless somebody cloned the MAC address.
If you try using the existence or non-existence of some network service to determine which network you're connected to, you can never be sure. For example, if you failed to map that network drive, all you know is that the network drive isn't available. You can't say for certain that you're not connected to the company LAN. Same is true if you use ping. Lack of response from a particular machine means only that the machine didn't respond.
Various things you can look at for differentiation:
DNS domain name (GetComputerNameEx)
MAC address of gateway (ping it, then GetIpNetTable)
Routing table(do you have a gateway and default route on the company LAN)
WNet discovered network resources (WNetOpenEnum, WNetEnumResource)
Ability to resolve external hostnames (try a 5-10 names like www.google.com, www.microsoft.com and so on, if one resolves you should have internet)
You'll have to decide how many indicators are "enough" to decide you're on one or the other LAN though if tests fail. Then keep retrying until you have a definite result.
http://msdn.microsoft.com/en-us/library/aa366071%28v=VS.85%29.aspx has a lot of network related functions that you can experiment with to create further indicators.
Is there an existing Linux/POSIX C/C++ library or example code for how to rebind a socket from one physical interface to another?
For example, I have ping transmitting on a socket that is associated with a physical connection A and I want to rebind that socket to physical connection B and have the ping packets continue being sent and received on connection B (after a short delay during switch-over).
I only need this for session-less protocols.
Thank you
Update:
I am trying to provide failover solution for use with PPP and Ethernet devices.
I have a basic script which can accomplish 90% of the functionality through use of iptables, NAT and routing table.
The problem is when the failover occurs, the pings continue being sent on the secondary connection, however, their source IP is from the old connection.
I've spoken with a couple of people who work on commercial routers and their suggestion is to rebind the socket to the secondary interface.
Update 2:
I apologise for not specifying this earlier. This solution will run on a router. I cannot change the ping program because it will run on the clients computer. I used ping as just an example, any connection that is not session-based should be capable of being switched over. I tested this feature on several commercial routers and it does work. Unfortunately, their software is proprietary, however, from various conversations and testing, I found that they are re-binding the sockets on failover.
As of your updated post, the problem is that changing the routing info is not going to change the source address of your ping, it will just force it out the second interface. This answer contains some relevant info.
You'll need to change the ping program. You can use a socket-per-interface approach and somehow inform the program when to fail over. Or you will have to close the socket and then bind to the second interface.
You can get the interface info required a couple of ways including calling ioctl() with the SIOCGIFCONF option and looping through the returned structures to get the interface address info.
I do't think that's quite a well-defined operation. the physical interfaces have different MAC addresses, so unless you have a routing layer mapping them (NAT or the like) then they're going to have different IP addresses.
Ports are identified by a triple of <IP addr, Port number, protocol> so if your IP address changes the port is going to change.
What are you really trying to do here?
I'm not at all sure what you're trying to accomplish, but I have a guess... Are you trying to do some kind of failover? If so, then there are indeed ways to accomplish that, but why not do it in the OS instead of the application?
On one end you can use CARP, and on the other you can use interface trunking/bonding (terminology varies) in failover mode.