[lwip-devel] [bug #27352] Change ip_addr from struct to typedef (u32_t)

[Simon Goldschmidt]

Follow-up Comment #10, bug #27352 (project lwip):

> Or I'm missing your point?

I guess so: when receiving UDP or RAW packets, we are passing the pointer to
a struct ip_addr and this pointer points into the pbuf. Now if the address is
unaligned in that packet, the information to access it packed is gone once we
use a normal pointer:

See this code from udp_input():
pcb->recv(pcb->recv_arg, pcb, p, &iphdr->src, src);

The application recv callback gets a 'struct ip_addr*' and wouldn't know that
this pointer has to be accessed packed!

> Doesn't everyone using 32-bit aligned processors use ETH_PAD 2
> to align everything?

That doesn't work for me as the DMA of the MAC would have to handle copying
from 32-bit aligned (internal buffer of the MAC) to 16-bit aligned (pbuf,
because of the 2-byte ETH_PAD).

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