[PACKET]: Add optional checksum computation for recvmsg
This patch is needed to make ISC's DHCP server (and probably other DHCP servers/clients using AF_PACKET) to be able to serve another client on the same Xen host. The problem is that packets between different domains on the same Xen host only have partial checksums. Unfortunately this piece of information is not passed along in AF_PACKET unless you're using the mmap interface. Since dhcpd doesn't support packet-mmap, UDP packets from the same host come out with apparently bogus checksums. This patch adds a mechanism for AF_PACKET recvmsg(2) to return the status along with the packet. It does so by adding a new cmsg that contains this information along with some other relevant data such as the original packet length. I didn't include the time stamp information since there is already a cmsg for that. This patch also changes the mmap code to set the CSUMNOTREADY flag on all packets instead of just outoing packets on cooked sockets. Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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