Merge branch 'devices-always-netif_f_lltx'

Peilin Ye says:

====================
devices always NETIF_F_LLTX

v1: https://lore.kernel.org/netdev/cover.1650580763.git.peilin.ye@bytedance.com/

change since v1:
  - deleted "depends on patch..." in [1/2]'s commit message

This patchset depends on these fixes [1], which has been merged into
net-next.  Since o_seqno is now atomic_t, we can always turn on
NETIF_F_LLTX for [IP6]GRE[TAP] devices, since we no longer need the TX
lock (&txq->_xmit_lock).

We could probably do the same thing to [IP6]ERSPAN devices as well, but
I'm not familiar with them yet.  For example, ERSPAN devices are
initialized as |= GRE_FEATURES in erspan_tunnel_init(), but I don't see
IP6ERSPAN devices being initialized as |= GRE6_FEATURES.  Where should we
initialize IP6ERSPAN devices' ->features?  Please suggest if I'm missing
something, thanks!

[1] https://lore.kernel.org/netdev/cover.1650575919.git.peilin.ye@bytedance.com/
====================

Link: https://lore.kernel.org/r/cover.1651207788.git.peilin.ye@bytedance.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

net/ipv4/ip_gre.c

@@ -748,6 +748,7 @@ static netdev_tx_t gre_tap_xmit(struct sk_buff *skb,
 static void ipgre_link_update(struct net_device *dev, bool set_mtu)
 {
 	struct ip_tunnel *tunnel = netdev_priv(dev);
+	__be16 flags;
 	int len;
 
 	len = tunnel->tun_hlen;
@@ -763,19 +764,15 @@ static void ipgre_link_update(struct net_device *dev, bool set_mtu)
 	if (set_mtu)
 		dev->mtu = max_t(int, dev->mtu - len, 68);
 
-	if (!(tunnel->parms.o_flags & TUNNEL_SEQ)) {
-		if (!(tunnel->parms.o_flags & TUNNEL_CSUM) ||
-		    tunnel->encap.type == TUNNEL_ENCAP_NONE) {
-			dev->features |= NETIF_F_GSO_SOFTWARE;
-			dev->hw_features |= NETIF_F_GSO_SOFTWARE;
-		} else {
+	flags = tunnel->parms.o_flags;
+
+	if (flags & TUNNEL_SEQ ||
+	    (flags & TUNNEL_CSUM && tunnel->encap.type != TUNNEL_ENCAP_NONE)) {
 		dev->features &= ~NETIF_F_GSO_SOFTWARE;
 		dev->hw_features &= ~NETIF_F_GSO_SOFTWARE;
-		}
-		dev->features |= NETIF_F_LLTX;
 	} else {
-		dev->hw_features &= ~NETIF_F_GSO_SOFTWARE;
-		dev->features &= ~(NETIF_F_LLTX | NETIF_F_GSO_SOFTWARE);
+		dev->features |= NETIF_F_GSO_SOFTWARE;
+		dev->hw_features |= NETIF_F_GSO_SOFTWARE;
 	}
 }
 
@@ -949,6 +946,7 @@ static void ipgre_tunnel_setup(struct net_device *dev)
 static void __gre_tunnel_init(struct net_device *dev)
 {
 	struct ip_tunnel *tunnel;
+	__be16 flags;
 
 	tunnel = netdev_priv(dev);
 	tunnel->tun_hlen = gre_calc_hlen(tunnel->parms.o_flags);
@@ -957,25 +955,21 @@ static void __gre_tunnel_init(struct net_device *dev)
 	tunnel->hlen = tunnel->tun_hlen + tunnel->encap_hlen;
 	dev->needed_headroom = tunnel->hlen + sizeof(tunnel->parms.iph);
 
-	dev->features		|= GRE_FEATURES;
+	dev->features		|= GRE_FEATURES | NETIF_F_LLTX;
 	dev->hw_features	|= GRE_FEATURES;
 
-	if (!(tunnel->parms.o_flags & TUNNEL_SEQ)) {
-		/* TCP offload with GRE SEQ is not supported, nor
-		 * can we support 2 levels of outer headers requiring
-		 * an update.
+	flags = tunnel->parms.o_flags;
+
+	/* TCP offload with GRE SEQ is not supported, nor can we support 2
+	 * levels of outer headers requiring an update.
 	 */
-		if (!(tunnel->parms.o_flags & TUNNEL_CSUM) ||
-		    (tunnel->encap.type == TUNNEL_ENCAP_NONE)) {
+	if (flags & TUNNEL_SEQ)
+		return;
+	if (flags & TUNNEL_CSUM && tunnel->encap.type != TUNNEL_ENCAP_NONE)
+		return;
+
 	dev->features |= NETIF_F_GSO_SOFTWARE;
 	dev->hw_features |= NETIF_F_GSO_SOFTWARE;
-		}
-
-		/* Can use a lockless transmit, unless we generate
-		 * output sequences
-		 */
-		dev->features |= NETIF_F_LLTX;
-	}
 }
 
 static int ipgre_tunnel_init(struct net_device *dev)

net/ipv6/ip6_gre.c

@@ -382,11 +382,6 @@ static struct ip6_tnl *ip6gre_tunnel_locate(struct net *net,
 		goto failed_free;
 
 	ip6gre_tnl_link_config(nt, 1);
-
-	/* Can use a lockless transmit, unless we generate output sequences */
-	if (!(nt->parms.o_flags & TUNNEL_SEQ))
-		dev->features |= NETIF_F_LLTX;
-
 	ip6gre_tunnel_link(ign, nt);
 	return nt;
 
@@ -1445,26 +1440,23 @@ static void ip6gre_tunnel_setup(struct net_device *dev)
 static void ip6gre_tnl_init_features(struct net_device *dev)
 {
 	struct ip6_tnl *nt = netdev_priv(dev);
+	__be16 flags;
 
-	dev->features		|= GRE6_FEATURES;
+	dev->features		|= GRE6_FEATURES | NETIF_F_LLTX;
 	dev->hw_features	|= GRE6_FEATURES;
 
-	if (!(nt->parms.o_flags & TUNNEL_SEQ)) {
-		/* TCP offload with GRE SEQ is not supported, nor
-		 * can we support 2 levels of outer headers requiring
-		 * an update.
+	flags = nt->parms.o_flags;
+
+	/* TCP offload with GRE SEQ is not supported, nor can we support 2
+	 * levels of outer headers requiring an update.
 	 */
-		if (!(nt->parms.o_flags & TUNNEL_CSUM) ||
-		    nt->encap.type == TUNNEL_ENCAP_NONE) {
+	if (flags & TUNNEL_SEQ)
+		return;
+	if (flags & TUNNEL_CSUM && nt->encap.type != TUNNEL_ENCAP_NONE)
+		return;
+
 	dev->features |= NETIF_F_GSO_SOFTWARE;
 	dev->hw_features |= NETIF_F_GSO_SOFTWARE;
-		}
-
-		/* Can use a lockless transmit, unless we generate
-		 * output sequences
-		 */
-		dev->features |= NETIF_F_LLTX;
-	}
 }
 
 static int ip6gre_tunnel_init_common(struct net_device *dev)