Adding flag both in katran and shiv to allow us to migrate FWM vips t…

…o also use dst port during hash

Summary:
Added a new flag for the balancer which will allow the fwm vips to use the port for hashing.

In shiv I'm setting this flag by adding a new scheduler which will be updated currently on runtime if the conditions of been fwm vip, using currently ch as scheduler and the startup flag is enabled.

Reviewed By: avasylev

Differential Revision: D51836527

fbshipit-source-id: 68224a3d18dcd28f1dc6f4d0c822f797e609cb84

katran/lib/bpf/balancer.bpf.c

@@ -749,7 +749,8 @@ process_packet(struct xdp_md* xdp, __u64 off, bool is_ipv6) {
       return XDP_PASS;
     }
 
-    if (!(vip_info->flags & F_HASH_DPORT_ONLY)) {
+    if (!(vip_info->flags & F_HASH_DPORT_ONLY) &&
+        !(vip_info->flags & F_HASH_SRC_DST_PORT)) {
       // VIP, which doesnt care about dst port (all packets to this VIP w/ diff
       // dst port but from the same src port/ip must go to the same real
       pckt.flow.port16[1] = 0;

katran/lib/bpf/balancer_consts.h

@@ -142,6 +142,9 @@
 #define F_LOCAL_VIP (1 << 5)
 // do a global lru lookup if we were unable to find the flow in the main lru map
 #define F_GLOBAL_LRU (1 << 6)
+// use both src and dst port for the hash calculation for vips which normally
+// wouldn't
+#define F_HASH_SRC_DST_PORT (1 << 7)
 // packet_description flags:
 // the description has been created from icmp msg
 #define F_ICMP (1 << 0)