Bug 66 - pasta --config-net accepts, but does not properly handle MTUs between 65522 and 65535
Summary: pasta --config-net accepts, but does not properly handle MTUs between 65522 a...
Status: CONFIRMED
Alias: None
Product: passt
Classification: Unclassified
Component: general (show other bugs)
Version: unspecified
Hardware: All Linux
: Normal normal
Assignee: David Gibson
URL:
Depends on:
Blocks: 65
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Reported: 2023-07-04 05:48 UTC by David Gibson
Modified: 2023-07-04 06:05 UTC (History)
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Description David Gibson 2023-07-04 05:48:18 UTC 
The MTU for the guest interface in pasta defaults to 65520 bytes.  However, it can be overridden with the --mtu / -m option.  conf.c will accept any value to this option between 68 and 65535 inclusive.  However, if values of 65522 or over are given, --config-net does not complete, and the tap interface is not up and has MTU 1500 within the guest.
Comment 1 David Gibson 2023-07-04 06:05:24 UTC 
This appears to be a consequence of the kernel limiting the MTU for tap devices to 65521 or less bytes.  It's another problem that would have shown up immediately if we detected and report netlink errors (see bug 60).
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