Re: [PATCH net v3] usbnet: cap max_mtu for drivers without bind callback

[email protected] Wed, 05 Aug 2026 01:20:15 +0000

Newsgroups	org.kernel.vger.linux-usb,org.kernel.vger.linux-kernel,org.kernel.vger.netdev,org.kernel.vger.stable
Message-ID	<178589281589.3863162.4194216540460778959.git-patchwork-notify@kernel.org>

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <[email protected]>:

On Fri, 31 Jul 2026 11:27:11 +0200 you wrote:
> usbnet_probe() initializes max_mtu to ETH_MAX_MTU and only caps it
> inside the if (info->bind) block. Drivers without a bind callback
> never enter this block, so max_mtu stays at ETH_MAX_MTU.
> 
> QEMU's usb-net device (0x0525/0xa4a2) is claimed by the cdc_subset
> driver which has no bind callback. The guest accepts any MTU from DHCP
> (e.g. 65520 from passt), leading to TCP segments that exceed the
> device's 2048-byte receive buffer and are silently dropped.
> 
> [...]

Here is the summary with links:
  - [net,v3] usbnet: cap max_mtu for drivers without bind callback
    https://git.kernel.org/netdev/net/c/1505b2cb6ae1

You are awesome, thank you!
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