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Re: [PATCH v2 1/2] net: Added mtu parameter to dev_forward_skb calls

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On Thu, 11 May 2017 15:46:27 +0200
Fredrik Markstrom <fredrik.markstrom@gmail.com> wrote:

> From: Fredrik Markström <fredrik.markstrom@gmail.com>
> 
> is_skb_forwardable() currently checks if the packet size is <= mtu of
> the receiving interface. This is not consistent with most of the hardware
> ethernet drivers that happily receives packets larger then MTU.

Wrong.

Hardware interfaces are free to drop any packet greater than MTU (actually MTU + VLAN).
The actual limit is a function of the hardware. Some hardware can only limit by
power of 2; some can only limit frames larger than 1500; some have no limiting at all.
Any application that should:
  * not expect packets larger than MTU to be received
  * not send packets larger than MTU
  * check actual receive size. IP protocols will do truncation of padded packets

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[PATCH v2 0/2] net: Set maximum receive packet size on veth interfaces Fredrik Markstrom <fredrik.markstrom@gmail.com> - 2017-05-11 16:00 +0200
  [PATCH v2 1/2] net: Added mtu parameter to dev_forward_skb calls Fredrik Markstrom <fredrik.markstrom@gmail.com> - 2017-05-11 16:00 +0200
    Re: [PATCH v2 1/2] net: Added mtu parameter to dev_forward_skb  calls Stephen Hemminger <stephen@networkplumber.org> - 2017-05-11 18:10 +0200
      Re: [PATCH v2 1/2] net: Added mtu parameter to dev_forward_skb calls Fredrik Markström <fredrik.markstrom@gmail.com> - 2017-05-11 21:20 +0200
        Re: [PATCH v2 1/2] net: Added mtu parameter to dev_forward_skb  calls Stephen Hemminger <stephen@networkplumber.org> - 2017-05-11 21:50 +0200
          Re: [PATCH v2 1/2] net: Added mtu parameter to dev_forward_skb calls Fredrik Markström <fredrik.markstrom@gmail.com> - 2017-05-12 16:40 +0200
        Re: [Bridge] [PATCH v2 1/2] net: Added mtu parameter to dev_forward_skb calls Teco Boot <teco@inf-net.nl> - 2017-05-12 10:10 +0200
          Re: [Bridge] [PATCH v2 1/2] net: Added mtu parameter to  dev_forward_skb calls Fredrik Markström <fredrik.markstrom@gmail.com> - 2017-05-12 14:50 +0200
  Support for VETH_MRU in libnl Fredrik Markstrom <fredrik.markstrom@gmail.com> - 2017-05-11 16:00 +0200

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