Issue connecting by DNS name with ".connect"
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Description
I have a small program I'm trying to use and connect to a linux/unix box with SSHClient. In this specific case, the remote system is a Raspberry Pi running raspbian (which I'm pretty sure has NO bearing on the issue).
My local network has a caching DNS that I use for internal addresses - I do not modify /etc/hosts, etc. In this case, ARP is used for the system to announce itself, and the caching DNS on my router will cache the name and IP as .local
I can always drop to a shell, and use the installed ssh client to connect to this system using ssh pi@.local without fail.
However, if I try to connect using:
client.connect('.local', username=user, password=pass, port=22)
will ALWAYS timeout.
If I use the IP address:
client.connect('10.0.0.50', username=user, password=pass, port=22)
it will IMMEDIATELY connect without issue.
If I modify this slightly like:
dns = socket.gethostbyname(".local")
client.connect(dns.strip', username=user, password=pass, port=22)
It will again immediately connect without issue
So this isn't a case of python not being able to resolve system names within it's libraries - this appears to be something within paramiko itself.
Here's the full sample code:
import paramiko
import socket
import getpass
import sys
dns = socket.gethostbyname("somesystem.local")
user="<username>"
pass="<password>"
client = paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
try:
# client.connect('10.0.0.53', username=user, password=pass, port=22)
# client.connect(socket.gethostbyname("somesystem.local"), username=user, password=pass, port=22)
client.connect(dns.strip(), username=user, password=pass, port=22)
print("Success on connection")
except paramiko.SSHException:
print("Connection Failed")
quit()
stdin, stdout, stderr = client.exec_command("ls -la; df -h")
for line in stdout.readlines():
print (line.strip())
client.close()
del client, stdout, stderr
sys.exit()
sys.exit()
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start at Paramiko's SSHClient.connect entry point and compare the reported behavior for the .local hostname with the socket.gethostbyname result shown in the sample. Reproduce the timeout using the provided code and verify that connecting by hostname succeeds consistently without manually resolving it first.
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Assessment
- Tech stack
- python
- Domain
- networking
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 25/100