Curt McDowell wrote:
Pedro Alves wrote
Seems like the right thing to do.
If the packing is removed from struct ip_addr, and struct
ip_addr2 is removed, then there is no need to memcpy anymore.
A simple:
sipaddr = hdr->sipaddr;
will do.
memcpy may still be needed because hdr->sipaddr is misaligned at +2 due to the
format of the ARP packet. My theory is that struct ip_addr2 was originally
invented because the 4-byte struct/uint32 copy was crashing on someone's 2-byte
aligned CPU!
Regards,
Curt McDowell
Broadcom Corp.
Either ip_addr2 or memcpy is needed.
The code "sipaddr = hdr->sipaddr;" would crash on any CPU which do not
support unaligned accesses.
The current ip_addr2 solution is technically more efficient than memcpy
since it copies the ip_addr with just two 16bit reads+writes.
The only solution which would be slightly more efficient is to copy
hdr->sipaddr to a 32bit register using two 16bit accesses, and then
write the 32bit register to sipaddr. But since this is not a critical
code path, it is more important to keep the code as clean as possible
rather than trying to save one single memory access.
The ip_addr2 solution makes the code nice and clean.
Regards,
Timmy Brolin
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