vrf: add CRC32c offload to device features

SCTP sockets originated in a VRF can improve their performance if CRC32c
computation is delegated to underlying devices: update device features,
setting NETIF_F_SCTP_CRC. Iterating the following command in the topology
proposed with [1],

 # ip vrf exec vrf-h2 netperf -H 192.0.2.1 -t SCTP_STREAM -- -m 10K

the measured throughput in Mbit/s improved from 2395 ± 1% to 2720 ± 1%.

[1] https://www.spinics.net/lists/netdev/msg486007.htmlSigned-off-by: NDavide Caratti <dcaratti@redhat.com>
Reviewed-by: NMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: NDavid Ahern <dsa@cumulusnetworks.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/vrf.c

@@ -1254,7 +1254,7 @@ static void vrf_setup(struct net_device *dev)
 
 	/* enable offload features */
 	dev->features   |= NETIF_F_GSO_SOFTWARE;
-	dev->features   |= NETIF_F_RXCSUM | NETIF_F_HW_CSUM;
+	dev->features   |= NETIF_F_RXCSUM | NETIF_F_HW_CSUM | NETIF_F_SCTP_CRC;
 	dev->features   |= NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_HIGHDMA;
 
 	dev->hw_features = dev->features;