Network path in linux

Path of UDP packet in linux kernel

I want to find the path of a UDP packet in the Linux kernel. For this, I want to read up on some documentation ( I have this so far, which is for TCP) and then have some printk statements in the relevant kernel functions to confirm that. I will do this by recompiling the kernel code. Is this the way to go about it? Do you have any suggestions/references?

W.R. Stevens, TCP/IP Illustrated, Volume II, gives a complete account for the BSD kernel, which I suspect would be just as informative, and no kernel meddling required.

4 Answers 4

Specifically answering your question, to understand UDP processing for IPv4 you can use ftrace, as is done here:

At the ingress (receiving side):

 96882 2) | ip_local_deliver_finish() < 96883 2) 0.069 us | raw_local_deliver(); 96884 2) | udp_rcv() < 96885 2) | __udp4_lib_rcv() < 96886 2) 0.087 us | __udp4_lib_lookup(); 96887 2) | __skb_checksum_complete_head() < 96888 2) | skb_checksum() < 96889 2) | __skb_checksum() < 96890 2) | csum_partial() < 96891 2) 0.161 us | do_csum(); 96892 2) 0.536 us | >96893 2) | csum_partial() < 96894 2) 0.167 us | do_csum(); 96895 2) 0.523 us | >96896 2) | csum_partial() < 96897 2) 0.158 us | do_csum(); 96898 2) 0.513 us | >96899 2) | csum_partial() < 96900 2) 0.154 us | do_csum(); 96901 2) 0.502 us | >96902 2) | csum_partial() < 96903 2) 0.165 us | do_csum(); 96904 2) 0.516 us | >96905 2) | csum_partial() < 96906 2) 0.138 us | do_csum(); 96907 2) 0.506 us | >96908 2) 5.462 us | > 96909 2) 5.840 us | > 96910 2) 6.204 us | > 

Another part of the tracing show below:

And for egress of networking code, some snippets are extracted below:

 4) 0.547 us | udp_poll(); 4) | udp_sendmsg() < 4) | udp_send_skb() < 4) 0.387 us | udp_error [nf_conntrack](); 4) 0.185 us | udp_pkt_to_tuple [nf_conntrack](); 4) 0.160 us | udp_invert_tuple [nf_conntrack](); 4) 0.151 us | udp_get_timeouts [nf_conntrack](); 4) 0.145 us | udp_new [nf_conntrack](); 4) 0.160 us | udp_get_timeouts [nf_conntrack](); 4) 0.261 us | udp_packet [nf_conntrack](); 4) 0.181 us | udp_invert_tuple [nf_conntrack](); 4) 0.195 us | udp_invert_tuple [nf_conntrack](); 4) 0.170 us | udp_invert_tuple [nf_conntrack](); 4) 0.175 us | udp_invert_tuple [nf_conntrack](); 4) | udp_rcv() < 4) + 15.021 us | udp_queue_rcv_skb(); 4) + 18.829 us | >4) + 82.100 us | > 4) + 92.415 us | > 4) | udp_sendmsg() < 4) | udp_send_skb() < 4) 0.226 us | udp_error [nf_conntrack](); 4) 0.150 us | udp_pkt_to_tuple [nf_conntrack](); 4) 0.146 us | udp_get_timeouts [nf_conntrack](); 4) 1.098 us | udp_packet [nf_conntrack](); 4) | udp_rcv() < 4) 1.314 us | udp_queue_rcv_skb(); 4) 3.282 us | >4) + 20.646 us | > 

The above is called function graph in ftrace:

And my bashscript for tracing udp are as follows (to be run as root):

#!/bin/bash mkdir /debug mount -t debugfs nodev /debug mount -t debugfs nodev /sys/kernel/debug echo udp_* >/debug/tracing/set_ftrace_filter echo function_graph >/debug/tracing/current_tracer echo 1 >/debug/tracing/tracing_on sleep 20 echo 0 >/debug/tracing/tracing_on cat /debug/tracing/trace > /tmp/tracing.out$$ 

Now the output file is locate inside the /tmp/tracing.out where is the shell script process. The purpose of 20 seconds is to allow userspace activities to happen — just starts lots of UDP activities at this point. You can also remove «echo udp_* >/debug/tracing/set_ftrace_filter» from above script, because the default is to trace everything.

Источник

What is the UNC network path to a folder shared via Samba?

I am trying to direct a scanner to scan directly to a shared folder on my home network. The scanner’s web service asks for the network path to my shared folder, and only accepts UNC as input, i. e. \\server\volume\path . My share is at //home//Public on a particular computer on my network. I know the IP address and netbios name of the computer, and know the shared folder path on my Ubuntu machine, but don’t know how to plug that in to come up with a valid UNC path to my shared folder. UPDATE: This is not a duplicate of the question that asked how to navigate to a samba share via command line of a share created in Nautilus. Instead, I was asking how to direct a web server to my samba share when the web server uses a Windows (UNC) input mask. I already knew the path to my samba share from the terminal and from other Linux devices on the network. I didn’t know how samba characterized this path to Windows machines or web servers that assume the Windows UNC file path naming conventions.

If it’s a duplicate, I’m not sure how to interpret the answer there. I have tried «smb:\\192.168.1.[xxx]\home[user]\Public» and just «\\192.168.1.[xxx]\home[user]\Public» as the Network path. Anything with «smb:» is rejected as an invalid path by the input mask. Any other path I put in is rejected also, with the message «invalid shared folder. check the network path and try again.»

On Linux you should use // . My idea was to determine full share name from Nautilus — for example smb://host_name_or_ip/share_name to write then it as \\host_name_or_ip\share_name on device.

Thanks, Norbert. That’s exactly what I tried. The web server considers them all invalid paths, however. The web server anticipates a Windows share, I think. but there has to be a way that Samba talks to Windows, as I can map a Windows drive to a Samba share without difficulty. I have a belief, or perhaps just a faith, that Samba somehow has a translation to Windowspeak that I can use in the input field to the web server.

Источник

How do I find the network path in Linux?

Network path or Shared path is a location where you can store files and other resources like your local path. One benefit of network share is that the files can be shared among multiple users.

How do I access a network share in Linux?

Access a Windows shared folder from Linux, using Nautilus

From the File menu, select Connect to Server. In the Service type drop-down box, select Windows share. In the Server field, enter the name of your computer. Click Connect.

How do I copy a full network path?

Any way to copy a full network path on Windows 10?

1. Open Command Prompt.
2. Type net use command and press Enter.
3. You should now have all mapped drives listed in the command result. You can copy the full path from the command line itself.
4. Or use net use > drives. txt command and then save the command output to a text file.

How do I trace a connection?

Traceroute is run from a command prompt or terminal window. On Windows, press the Windows key, type Command Prompt, and press Enter to launch one. (On Mac or Linux, run traceroute howtogeek.com instead.) You’ll gradually see the route take form as your computer receives responses from the routers along the way.

How do I find the path of a mapped network drive?

You can view a list of mapped network drives and the full UNC path behind them from a command prompt.
…
Find the full UNC path of a mapped drive

1. Hold down the Windows key + R, type cmd and click OK.
2. In the command window type net use then press Enter.
3. Make a note of the required path then type Exit then press Enter.

What protocol is SMB?

The Server Message Block (SMB) Protocol is a network file sharing protocol, and as implemented in Microsoft Windows is known as Microsoft SMB Protocol. The set of message packets that defines a particular version of the protocol is called a dialect. The Common Internet File System (CIFS) Protocol is a dialect of SMB.

What is the port number for SMB?

As such, SMB requires network ports on a computer or server to enable communication to other systems. SMB uses either IP port 139 or 445.

How do I connect to a file server?

Connect to a file server

1. In the file manager, click File ▸ Connect to Server.
2. Enter the server address, select the type of server, and enter any additional information as required. Then click Connect. …
3. A new window will open showing you the files on the server.

Источник

How do I find network location in Linux?

Right click on the Computer icon on the desktop. From the drop down list, choose Map Network Drive. Pick a drive letter that you want to use to access the shared folder and then type in the UNC path to the folder. UNC path is just a special format for pointing to a folder on another computer.

How do I access a shared folder in Linux?

Access a Windows shared folder from Linux, using Nautilus

1. Open Nautilus.
2. From the File menu, select Connect to Server.
3. In the Service type drop-down box, select Windows share.
4. In the Server field, enter the name of your computer.
5. Click Connect.

How do I connect to a Linux server?

Connect to a file server

1. In the file manager, click Other Locations in the sidebar.
2. In Connect to Server, enter the address of the server, in the form of a URL. Details on supported URLs are listed below. …
3. Click Connect. The files on the server will be shown.

Can I access Windows files from Linux?

Because of the nature of Linux, when you boot into the Linux half of a dual-boot system, you can access your data (files and folders) on the Windows side, without rebooting into Windows. And you can even edit those Windows files and save them back to the Windows half.

What is fstab in Linux?

Your Linux system’s filesystem table, aka fstab , is a configuration table designed to ease the burden of mounting and unmounting file systems to a machine. … It is designed to configure a rule where specific file systems are detected, then automatically mounted in the user’s desired order every time the system boots.

What is CIFS in Linux?

Common Internet File System (CIFS), an implementation of the Server Message Block (SMB) protocol, is used to share file systems, printers, or serial ports over a network. Notably, CIFS allows sharing files between Linux and Windows platforms regardless of version.

How do I see network issues in Linux?

How to troubleshoot network connectivity with Linux server

1. Check your network configuration. …
2. Check the network configuration file. …
3. Check the servers DNS records. …
4. Test the connection both ways. …
5. Find out where the connection fails. …
6. Firewall settings. …
7. Host status information.

How do I find the Linux version?

Check os version in Linux

1. Open the terminal application (bash shell)
2. For remote server login using the ssh: ssh [email protected]
3. Type any one of the following command to find os name and version in Linux: cat /etc/os-release. lsb_release -a. hostnamectl.
4. Type the following command to find Linux kernel version: uname -r.

How do I check network parameters in Linux?

Computer loaded with Linux Operating System can also be a part of network whether it is small or large network by its multitasking and multiuser natures.
…

1. ifconfig. …
2. PING Command. …
3. TRACEROUTE Command. …
4. NETSTAT Command. …
5. DIG Command. …
6. NSLOOKUP Command. …
7. ROUTE Command. …
8. HOST Command.

Источник

Network routes in Linux

Network routes on Linux servers are the paths or gateways packets should follow to reach their destinations. Routes can be configured on interface level and system level. The default route is also known as default gateway is the IP where the packet should discover their path if the current network or interface (from which packet originated on the server) does not know the path for destination IP. This article is about discussing network routes in Linux. It will cover how to define the network route for the network interface, where and how to define the default route or default gateway in Linux etc.

How to check current routes on system?

Current routes on system can be viewed using below commands.

# ip route default via 172.31.0.1 dev eth0 172.31.0.0/20 dev eth0 proto kernel scope link src 172.31.4.137

# netstat -r Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface default ip-172-31-0-1.a 0.0.0.0 UG 0 0 0 eth0 172.31.0.0 * 255.255.240.0 U 0 0 0 eth0

# routel target gateway source proto scope dev tbl default 172.31.0.1 eth0 172.31.0.0/ 20 172.31.4.137 kernel link eth0 127.0.0.0 broadcast 127.0.0.1 kernel link lo local 127.0.0.0/ 8 local 127.0.0.1 kernel host lo local ----- output clipped -----

You can observe 172.31.0.1 is defined as default gateway on above system.

How to configure static route in Linux?

In RHEL: You need to edit below parameters in the config file /etc/sysconfig/network-scripts/route-ethX .

GATEWAY=10.10.0.1 NETMASK=255.0.0.0 IPADDR=10.10.0.22

• gateway is the default gateway for this interface
• the netmask is a subnet mask value
• ipaddr is the IP address of this interface

Caution : Do not change gateways on live production system.

In Debian: You can put your route in the file /etc/network/interfaces under the intended interface.

auto eth0 iface eth0 inet static address 10.10.0.22 netmask 255.0.0.0 up route add -net 10.10.0.0 netmask 255.0.0.0 gw 10.10.0.1

In all Linux systems you can use ip route command to define the static route. Command syntax is :

# ip route ip-address via dest-address

where, ip-address is IP of host or interface and dest-address is next HOP address i.e. route IP

How to configure default gateway in Linux?

In RHEL: Define default gateway IP against GATEWAY parameter in /etc/sysconfig/network file and then restart network service.

In Debian: Define default gateway IP against gateway parameter in /etc/network/interfaces file and then restart network service.

Or you can try these commands on any Linux (ex gateway as 10.10.0.1).

# ip route add default via 10.10.0.1 # route add default gw 10.10.0.1

Once set verify the default gateway with commands shown at the beginning of this article.

Источник