etharp_query() queues packets, instead of sending, if a relevant arp-request is
pending.
Code walks the packet (a pbuf chain) to determine whether any pbufs are marked
'volatile': If so, we cannot simply enqueue the packet, and instead allocate a
new pbuf from RAM, copying the original packet, and enqueueing this new pbuf.
The bug here is that the allocation refers to the tot_len field of a temp pbuf*,
'p', instead of the head, 'q'.
In the case where the first pbuf of the chain is non-volatile but the second pbuf
*is* volatile, then we'll request an allocation that uses the tot_len field of
the second pbuf. If the first pbuf is non-zero length, the allocated pbuf (chain)
will be too small to allow the copy.
Signed-off-by: goldsimon <goldsimon@gmx.de>
lwIP aims to support zero-copy TX, and thus, must internally handle
all cases that pbufs are referenced rather than copied upon low-level
output. However, in the current situation, the arp/ndp packet queuing
routines conservatively copy entire packets, even when unnecessary in
cases where lwIP is used in a zero-copy compliant manner. This patch
moves the decision whether to copy into a centralized macro, allowing
zero-copy compliant applications to override the macro to avoid the
unnecessary copies. The macro defaults to the safe behavior, though.
- Code duplication with etharp_raw()
- No great effect on perfomance
- May make reworking PBUF handling code more complicated (see bug #49914)
- The check for p->type == PBUF_REF is a strange special case, too
- Simon also voted to remove it
Eliminate ETHADDR32_COPY macro - it cannot be used in ETH_PAD_SIZE case. I could have kept it by defining it to ETHADDR16_COPY in case of ETH_PAD_SIZE, but I did not consider it worth another #ifdef mess.
Let lwip use functions/macros prefixed by lwip_ internally to avoid naming clashes with external #includes.
Remove over-complicated #define handling in def.h
Make functions easier to override in cc.h. The following is sufficient now (no more LWIP_PLATFORM_BYTESWAP):
#define lwip_htons(x) <your_htons>
#define lwip_htonl(x) <your_htonl>
