[lwip-devel] [bug #49292] IP_HLEN seems to be incorrect in ip4.h

[Michael Bechard]

URL:
  <http://savannah.nongnu.org/bugs/?49292>

                 Summary: IP_HLEN seems to be incorrect in ip4.h
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: mtbowler416
            Submitted on: Fri 07 Oct 2016 02:32:57 PM GMT
                Category: IPv4
                Severity: 3 - Normal
              Item Group: Change Request
                  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:

In file src/include/lwip/prot/ip4.h, IP_HLEN is defined as 20, and the comment
right above this line says it should be the same as "sizeof(struct ip_hdr)".
However, sizeof(struct ip_hdr) returns 28, which is also the value I get when
counting up the bytes in the ip_hdr definition.

I noticed this when using a udp packet for TFTP, and realized the udp_hdr
destination port was being overwritten. Changing the length to 28 fixes this.




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