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Wrong MTU for IEEE802.15.4 #622

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thvdveld opened this issue May 30, 2022 · 1 comment · Fixed by #857
Closed

Wrong MTU for IEEE802.15.4 #622

thvdveld opened this issue May 30, 2022 · 1 comment · Fixed by #857
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@thvdveld
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When calling interface_mtu for the IEEE802154 medium, a value of 123 is returned, instead of 125 or 127 (when including the IEEE80254 checksum field). I just noticed it now, because before #611, the header Ethernet header size was added to the MTU, so returning 137 bytes for IEEE802154.
@thvdveld
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Currently, #580 adds a workaround, however, this is not a correct fix.

https://github.com/thvdveld/smoltcp/blob/f3310e63f4b014cc7f5f04ad9393e13602e7c163/src/phy/raw_socket.rs#L36-L40

thvdveld added a commit to thvdveld/smoltcp that referenced this issue Nov 17, 2023
@thvdveld
fix: clarify mtu+=2 for IEEE802154
969f32d 
This fixes smoltcp-rs#622, where at the time of writing, it was not clear why
SIOCGIFMTU returned 123 instead of the more logical 125 or 127 (with
FCS).
@thvdveld thvdveld mentioned this issue Nov 17, 2023
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fix: clarify mtu+=2 for IEEE802154 thvdveld/smoltcp
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@Dirbaio @thvdveld