NAT encapsulated flows have one 5-tuple per sled

[FelixMcFelix]

dendrite/dpd/p4/sidecar.p4

Lines 515 to 516 in f9fba02

	hdr.udp.src_port = GENEVE_UDP_PORT;
	hdr.udp.dst_port = GENEVE_UDP_PORT;

dendrite/dpd/p4/sidecar.p4

Line 527 in f9fba02

hdr.ipv6.next_hdr = IPPROTO_UDP;

dendrite/dpd/p4/sidecar.p4

Lines 529 to 530 in f9fba02

	hdr.ipv6.src_addr = 0;
	hdr.ipv6.dst_addr = meta.nat_ingress_tgt;

I think as a consequence every packet from the external network to a guest will have the same flowhash when seen by the NIC, and thus land on the same ring and softring. Packets will at least be hashed among viona rings properly, since we're using the inner 5-tuple at that point.

We probably need to hash (some of?) the inner 5-tuple and place it in the encap's UDP source port field.