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arp/ndp: allow overriding the decision to copy pbufs

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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.
This commit is contained in:
David van Moolenbroek
2017-02-27 14:43:58 +00:00
committed by goldsimon
parent 27c835aa56
commit d3fc398580
3 changed files with 22 additions and 8 deletions
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7
src/core/ipv4/etharp.c
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@@ -996,13 +996,12 @@ etharp_query(struct netif *netif, const ip4_addr_t *ipaddr, struct pbuf *q)
/* entry is still pending, queue the given packet 'q' */
struct pbuf *p;
int copy_needed = 0;
/* IF q includes a PBUF_REF, PBUF_POOL or PBUF_RAM, we have no choice but
* to copy the whole queue into a new PBUF_RAM (see bug #11400)
* PBUF_ROMs can be left as they are, since ROM must not get changed. */
/* IF q includes a pbuf that must be copied, copy the whole chain into a
* new PBUF_RAM. See the definition of PBUF_NEEDS_COPY for details. */
p = q;
while (p) {
LWIP_ASSERT("no packet queues allowed!", (p->len != p->tot_len) || (p->next == 0));
if (p->type != PBUF_ROM) {
if (PBUF_NEEDS_COPY(p)) {
copy_needed = 1;
break;
}