Bugs item #2990815, was opened at 2010-04-22 04:04
Message generated for change (Comment added) made by dfandrich
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Category: libcurl
Group: wrong behaviour
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Paul (codemonkey535)
Assigned to: Daniel Stenberg (bagder)
Summary: "interface" option does not work on an IPv6 VLAN

Initial Comment:
Attempting to bind a curl operation to take place using a VLAN interface specified by name does not work.

I am using libcurl 7.20.1 on a linux 2.6.31 kernel.

Do the following to create a VLAN:
vconfig add eth0 2
ifconfig eth0.2 up
ifconfig eth0.2 add fc00::2/64

Then assuming there is a web server at fc00::1 also on VLAN 2
> curl -g --interface eth0.2 http://[fc00::1]/index.html
should work but instead it reports
"cannot bind to eth0.2"

If instead I bind to the interface by using its IP address
> curl -g --interface fc00::2 http://[fc00::1]/index.html
then it seems to work.

And a third option which also works is to not specify the interface but to allow the routing table to determine which interface to use.
> curl -g http://[fc00::1]/index.html

However, neither of options 2 or 3 are good enough for my application since it is theoretically possible for the same local IP address to exist on different VLANs (which breaks option 2) or for the same remote IP address to be accessible via different VLANS (which breaks option 3)

If using an IPv4 address scheme it seems to work in both cases: interface IP or interface name.

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>Comment By: Dan Fandrich (dfandrich)
Date: 2010-04-22 11:13

Message:
Have you tried specifying a scope identifier? Something like this: curl -g
'http://[fc00::1%254]/index.html' I don't think specifying --interface
works to specify the IPv6 scope. See curl --manual for more discussion on
scope identifiers.

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Received on 2010-04-22