ipvs: optimize checksums for apps

 	Avoid full checksum calculation for apps that can provide
info whether csum was broken after payload mangling. For now only
ip_vs_ftp mangles payload and it updates the csum, so the full
recalculation is avoided for all packets.

 	Add CHECKSUM_UNNECESSARY for snat_handler (TCP and UDP).
It is needed to support SNAT from local address for the case
when csum is fully recalculated.

Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>

1 files changed, 10 insertions, 2 deletions

diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
index 6e8a6192e574..adcdba9dd183 100644
--- a/include/net/ip_vs.h
+++ b/include/net/ip_vs.h
@@ -597,11 +597,19 @@ struct ip_vs_app {
         __be16                  port;           /* port number in net order */
         atomic_t                usecnt;         /* usage counter */
 
-        /* output hook: return false if can't linearize. diff set for TCP.  */
+        /*
+         * output hook: Process packet in inout direction, diff set for TCP.
+         * Return: 0=Error, 1=Payload Not Mangled/Mangled but checksum is ok,
+         *         2=Mangled but checksum was not updated
+         */
         int (*pkt_out)(struct ip_vs_app *, struct ip_vs_conn *,
                        struct sk_buff *, int *diff);
 
-        /* input hook: return false if can't linearize. diff set for TCP. */
+        /*
+         * input hook: Process packet in outin direction, diff set for TCP.
+         * Return: 0=Error, 1=Payload Not Mangled/Mangled but checksum is ok,
+         *         2=Mangled but checksum was not updated
+         */
         int (*pkt_in)(struct ip_vs_app *, struct ip_vs_conn *,
                       struct sk_buff *, int *diff);