[lwip-devel] [bug #55030] Ethernet SAP stored backwards on Big endian system ?

[Ivan Warren]

URL:
  <https://savannah.nongnu.org/bugs/?55030>

                 Summary: Ethernet SAP stored backwards on Big endian system ?
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: ivanw
            Submitted on: Thu 15 Nov 2018 03:31:58 PM UTC
                Category: Platform ports
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None
            lwIP version: git head

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Details:

On my big endian system, I'm getting the following (for frames sent by LWIP -
in this case the DHCP client) :

LCS : 0000 : 01620100 FFFFFFFF FFFFFA40 4BB43CE8 00084500 50010000 0000FF11
9DBA0000
LCS : 0020 : 0000FFFF FFFF4400 43003C01 DCAC0101 06008127 00000000 00000000
00000000
LCS : 0040 : 00000000 00000000 0000FA40 4BB43CE8 00000000 00000000 00000000
00000000
LCS : 0060 : 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000
LCS : 0080 : 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000
LCS : 00A0 : 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000
LCS : 00C0 : 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000
LCS : 00E0 : 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000
LCS : 0100 : 00000000 00000000 00000000 00000000 00000000 00000000 00006353
82633501
LCS : 0120 : 01390205 DC370401 031C06FF 00000000 00000000 00000000 00000000
00000000
LCS : 0140 : 00000000 00000000 00000000 00000000 00000000 00000000 00000000
00000000

(This a is debug dump from my network interface driver... Ignore the 1st 4
bytes, they are for the output hardware).

The problem is : The SAP field (ETH Frame + 12 is inverted ! It should be 0800
(IP), not 0008 - making it a 802.3 Frame of length 8).

I somehow suspect that this field was inverted somewhere, but I cannot make
out where it could happen. (htons and PP_HTONS should be good)




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