net: introduce a netdev feature for UDP GRO forwarding

Introduce a new netdev feature, NETIF_F_GRO_UDP_FWD, to allow user
to turn UDP GRO on and off for forwarding.
Defaults to off to not change current datapath.

Suggested-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Alexander Lobakin <alobakin@pm.me>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/netdev_features.h

@@ -84,6 +84,7 @@ enum {
 	NETIF_F_GRO_FRAGLIST_BIT,	/* Fraglist GRO */
 
 	NETIF_F_HW_MACSEC_BIT,		/* Offload MACsec operations */
+	NETIF_F_GRO_UDP_FWD_BIT,	/* Allow UDP GRO for forwarding */
 
 	/*
 	 * Add your fresh new feature above and remember to update
@@ -157,6 +158,7 @@ enum {
 #define NETIF_F_GRO_FRAGLIST	__NETIF_F(GRO_FRAGLIST)
 #define NETIF_F_GSO_FRAGLIST	__NETIF_F(GSO_FRAGLIST)
 #define NETIF_F_HW_MACSEC	__NETIF_F(HW_MACSEC)
+#define NETIF_F_GRO_UDP_FWD	__NETIF_F(GRO_UDP_FWD)
 
 /* Finds the next feature with the highest number of the range of start till 0.
  */
@@ -234,7 +236,7 @@ static inline int find_next_netdev_feature(u64 feature, unsigned long start)
 #define NETIF_F_SOFT_FEATURES	(NETIF_F_GSO | NETIF_F_GRO)
 
 /* Changeable features with no special hardware requirements that defaults to off. */
-#define NETIF_F_SOFT_FEATURES_OFF	NETIF_F_GRO_FRAGLIST
+#define NETIF_F_SOFT_FEATURES_OFF	(NETIF_F_GRO_FRAGLIST | NETIF_F_GRO_UDP_FWD)
 
 #define NETIF_F_VLAN_FEATURES	(NETIF_F_HW_VLAN_CTAG_FILTER | \
 				 NETIF_F_HW_VLAN_CTAG_RX | \

net/ethtool/common.c

@@ -68,6 +68,7 @@ const char netdev_features_strings[NETDEV_FEATURE_COUNT][ETH_GSTRING_LEN] = {
 	[NETIF_F_HW_TLS_RX_BIT] =	 "tls-hw-rx-offload",
 	[NETIF_F_GRO_FRAGLIST_BIT] =	 "rx-gro-list",
 	[NETIF_F_HW_MACSEC_BIT] =	 "macsec-hw-offload",
+	[NETIF_F_GRO_UDP_FWD_BIT] =	 "rx-udp-gro-forwarding",
 };
 
 const char