I have machine with two Ethernet network interfaces. eno0 and eno1. eno0 is where the internet is plugged in and eno1 has a connected Ethernet device. I got its IP through Link-Local Address method and it's 168.254.80.23. I would like to send a packet to port 5000.
I would like to use Rust's UdpSocket to connect to this address and given port and send some packet. One such packet is already correctly described in the variable buf_with_message:
let sock = UdpSocket::bind("0.0.0.0:0"); //Let system assign me an ip and port
sock.connect(("168.254.80.23",5000)); // Connect to device ip and pre-designated port 5000
sock.send(&buf_with_message).unwrap(); //Send the packet
That connection occurs as it should, but the packet is send over eno0 instead of eno1. I have no idea how to specify the interface it should use. I have found some answers that in C SO_BINDTODEVICE could be used to do this.
I have also tried assigning an IP to the interface through
sudo ifconfig eno1 192.0.2.10
and then changing the 0.0.0.0 address in UdpSocket::bind to this new address with no positive result.
I see a potential solution to go straight to raw sockets using the pnet crate but I think that would be overkill.
I am aware that RFC 3927 warns against hosts with multiple interfaces, but I didn't find any options for an alternative without ditching LLA and implementing a DHCP server.
I have started a DHCP server and I am communication over the IP that is given through DHCP. I have no idea why LLA assigned IP doesn't work when DHCP does, but it works for now.
Related
If I connect a device via ethernet onto a switch, and do not receive an IP address via DHCP, how do I determine what the correct settings for that network should be, i.e. how do I choose a static IP address, subnet mask and gateway?
The specifics in my case are that I have an NVR with an 8 port POE switch that has 3 cameras plugged into it. I plugged my Windows 10 PC into the switch, expecting to be issued an IP address from the NVR via DHCP, but my PC was not given an IP. Perhaps the NVR assigns IPs via BOOTP? I want to get onto the network, probably by assigning a static IP that's not already used, then determine the IPs of the cameras so I can stream video from them directly using VLC.
Can I use tcpdump? There should be plenty of traffic from the cameras to the NVR.
how do I choose a static IP address, subnet mask and gateway?
The short answer - this should be done by your network administrator. If you are the network administrator - you should. But seems that you are connecting to the network you know nothing about.. Anyway here are some points that perhaps can help you.
There is a special thing called ARP Duplicate Address Detection (DAD). In Linux you can check if the particular IP is occupied in your broadcast segment with help of arping utility. From MAN page:
-D
Duplicate address detection mode (DAD). See RFC2131, 4.4.1.
Returns 0, if DAD succeeded i.e. no replies are received.
So if IP address is occupied you will see something like:
-bash-4.4# arping -D 10.0.99.99 -I eth0
ARPING 10.0.99.99 from 0.0.0.0 eth0
Unicast reply from 10.0.99.99 [DE:AD:BE:EF:00:8D] 1.274ms
Sent 1 probes (1 broadcast(s))
Received 1 response(s)
If this IP address is vacant, you'll see no responses. Read about ARP ping in Windows.
Also you can inspect the network through the tcpdump (to see some IP addressing info at least in broadcast packets), nmap and some other scanning utilities, but this topic is too broad (and at the same time it's well disclosed on the Internet). Btw you have to consider network architecture difficulties: vlan and so on.
I'm trying to send UPD packets from node A to node B, both are connected to internet through different routers.
I am able to send (and receive) UDP packets between them when they connected on the same network by giving the local destination ip adddress (192.168..) and port number.
Now I'm finding the dynamic ip address of node B using www.whatismyip.com and consider it as w.x.y.z
When I send the packets from A to this destination, I'm unable to receive them at B. I've also setup port forwarding on both the routers.
This is completely new to me. Is there is something else that needs to be done when I want to send packets to a node connected on another network? Please help!!
I can suggest something to check:
Port Forwarding in both the router are configured for the UDP protocol?
If you ping the remote address w.x.y.z, you receive a response? (check if the routers are configured to do so)
Verify also if there are firewall that block the UDP packet that arrives from the Internet (on the routers or on the target machine).
The thing that you can not receive them at B is because NAT will filter all the messages if you haven't build a connection in the netfilter's table. The way to solve the problem is to use a port mapping like UPNP or NAT-PMP. In this way, the destination node's specific port will receive any message from WLAN and send it to this node. But this needs your router support these protocols, if not, maybe you need to use ICE as a realy server to realize it.
I'm trying to get Age of Empires II (AoE2) to work on my LAN. AoE2 is notorious for it's connectivity problems on modern systems, probably because it used a now deprecated network framework called DirectPlay (in DX9) and the code probably wasn't robust back in the day either.
When I host a LAN game on a computer (win7) for AoE2, Wireshark shows my computer sending a couple packets via SSDP protocol to the multicast address 239.255.255.250. This actually goes to my router (for forwarding I assume) and my router returns a packet using ICMP protocol that says "Destination unreachable (Port unreachable)". Because nothing is forwarded to the other computers on the network, they can't see the game that the host has created.
I think I need to get the application/windows7 to send the packet as something like a broadcast, or I need to get the router to broadcast packets going to that multicast address. Does anyone have thoughts or suggestions on how to do this?
My router/gateway is running DD-WRT firmware v24-sp2.
My first guess is you're using wifi, by default most systems disable multicast on wifi because it can have a detrimental effect on the time slicing that wifi uses. however for just a couple machines it shouldn't be an issue.
here's how to disable multicasting but it should point you in the right direction for enabling it: ddwrt multicast
Secondly make sure they are all in the same VLAN a VLAN is defined as a "broadcast domain" meaning machines on separate VLANs will NEVER get broadcast or multicast from other VLANs without some trickery.
Lastly make sure you've enabled multicasting between LAN ports I believe the option is "multicast forward"
Edit: Just a few things to add to the list in case others have this issue. Broadcasting doesn't exist in ipv6, also a machine running ipv6 MAY NOT see broadcasts from a machine on ipv4 and a machine on ipv4 WILL NOT see multicasts to an ipv6 multi-cast address.
Have you tried LogMeIn Hamachi?
Is not a LAN client itself but it creates a fake Online-LAN and gives you a working IP that will allow you to play with who have it.
I have an application that uses QUdpSocket to send broadcast packets. The machine sending the packets has several network interfaces.
Unfortunately, I haven't been able to figure out how to get QUdpSocket to use the right network interface. Is there an option somewhere that allows me to specify exactly which interface to use for sending the packets?
Every subnet has its own broadcast address. So I think you can send broadcast packets 'directly' to the addresses like 10.255.255.255 or 192.168.255.255.
You are actually choosing which network to listen to in the first argument of bind function, address. If you are choosing for example QHostAddress::AnyIPv4 it means that no matter from which interface (better to say as a result of which IP address) the packet is received, the program should catch it. Otherwise you can enter an IP address (or a broadcast address) to which the packet should be sent.
For debugging and verification of it you can use netstat to list open ports as explained here:
https://superuser.com/questions/529830/get-a-list-of-open-ports-in-linux
In the result of netstat command, Local Address is what you are looking for, specifying which address is being listened to.
NOTE: The address of localhost in Local Address (e.g.: 0.0.0.0 or 127.0.0.1) means any Local Address is acceptable.
If I have two internal computers connecting to the same external IP address through a NAT router, how is the router able to get the traffic to the correct internal computer? It is my understanding that NAT forwards incoming packets to the computer that recently sent outgoing packets to the [incoming packet's] sender's IP address. Since both computers are sending to the same address, does the router forward the packet to both? If that is the case, is it the responsibility of the client software to determine which packets are relevant?
Is it possible if both computers are attempting to connect to the same port?
When you open a socket, you need to address a port of the destination system and open a conjugate listening port on your own system to receive any response. You have to send the destination system your listening port.
Having more than one system using the same modem
When you start a web browser, and go to www.google.com:80, your browser obtains/searches for a free non-system conjugate port from the system for listening. Let us say, the conjugate port is 10000. The listener port is for receiving the http stream back from google.
Then your kid sitting next to you incidentally also browses www.google.com:80 and his/her google session of the play station or xbox-whatever also incidentally is assigned conjugate port 10000.
Both of you are sitting behind a cable modem, and behind the cable modem is your wireless router. And both of your systems are behind the wireless router - All sitting in that sequence, network topology-wise.
To prevent port address collision on the router/modem
Let us say that your cable company DHCP assigns your modem ip4 adress 72.72.72.72. But your wireless router DHCP assigns 192.168.0.10 to your system and to 192.168.0.11 to your kid's system.
When the frame carrying the information of your listener ports passes thro your NAT router, it would translate either one or both listening- ports. Let's say port 15000 for your page and port 16000 for your kid's page.
Your wireless router then sends your requests to google server as coming from 72.72.72.72:15000 and 72.72.72.72:16000.
The google server then responds individually to 72.72.72.72:15000 and 72.72.72.72:16000 and when you wireless router encounters the response, it reaches into the mapping that it has stored and translates 72.72.72.72:15000 to 192.168.0.10:10000 to reach your system but translates 72.72.72.72:16000 to 192.168.0.11:10000 to reach your kid's system.
Running web/game/ftp/etc servers
But what if you have a web server or an ftp server running on your system. What if you have two systems and both have a web server and both web servers are listening on port 80?
Let us say the local ip addresses registered/assigned with your wireless router of your first web server system is 192.168.0.30 and your second web server system is 192.168.0.40.
The wireless router would have a configuration web page usually by default 192.168.0.1:80, unless you changed it. There would be a tab to on the page where you could define/reserve application port mappings.
You could register with your wireless router to reserve the mapping
192.168.0.30:80 => outgoing port 8080
192.168.0.40:80 => outgoing port 8088
So that you have to phone your friends your web/game servers are addressable through
72.72.72.72:8080 and 72.72.72.72:8088 respectively,
where the wireless router would preclude its port 8080 and 8088 from its own dynamic NAT usage.
Of course, 72.72.72.72 is as good as only before your ISP DHCP decide to renew the ip4 address of your modem to say, 72.72.90.200. After which you would have to phone/email your friends and say
Hey, the servers' addresses have changed to 72.72.90.200:8080 and 72.72.90.200:8088 respectively. Or you could subscribe to dynamic dns (ddns) service to use a named domain where the ddns service will need you to install a simple heartbeat utility on your system to help them monitor the address variation. DDNS translation is a separate issue/strategy.
NAT modems
Newer ISP contracts supply you with a modem that has NAT. If so, you have to switch off either the one on your modem or the one on your wireless router. You should not use both - what's the point in translating twice because NAT is simply to prevent address collision. When you switch off NAT from your wireless router, it can operate as a hub switch and not a router anymore so that you could connect it to the modem using one of its LAN socket instead of thro its WAN socket.
The router manages "source" ports that are separate for each computer. While you may be connecting to port 80 on the "destination" the router may assign the source port to some high number port.
Wikipedia sums it up as
Network address translation involves
re-writing the source and/or
destination IP addresses and usually
also the TCP/UDP port numbers of IP
packets as they pass through the NAT.
Checksums (both IP and TCP/UDP) must
also be rewritten to take account of
the changes.
Already good answers are provided, but here is another example:
HOST A addr HOST B addr
10.1.0.2:4040 10.1.0.3:4040
-----------------------------------------
NAT 200.50.50.28:4040 200.50.50.28:4041 (what external host sees)
200.50.50.28 is router's global (internet) IP.
Every port number is unique in the NAT table. And of course the router does all the dirty job of modifying the source and destination addresses transparently.
It uses different ports for incoming external traffic, and the NAT then routes the packets on one port to one internal IP address, and the packets from the other port to the other internal IP address... The iniital request from each internal computer, when it goes through the NAT on the way out, establishes which port will be used for the incoming traffic from the external ip address, and it tells the external server what port to send it's traffic back on for that connection.
RFC3022 provides a lot of information on how this works
Since public facing or external IP Address that was given by Internet Service Provider (ISP) has been discussed, I would like to add on this.
You can ask your ISP to have your public IP Address not change. It will become static, so that you do not have to inform your friends to change the IP Address if they want to access your server inside your Network Address Translator (NAT).
As of this writing, static IP Address cost around 100 bucks. Most of the ISP they call it business account.
You can determine your public facing IP Address by googling "what is my ip address".