netdev - Re: [PATCH v3 net-next 01/10] net: introduce mangleid

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Message-ID: <3892a971-6f0d-405a-a938-a8439e89b329@redhat.com>
Date: Mon, 19 Jan 2026 11:13:53 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
 Jakub Kicinski <kuba@...nel.org>, Simon Horman <horms@...nel.org>,
 Donald Hunter <donald.hunter@...il.com>, Andrew Lunn
 <andrew+netdev@...n.ch>, Shuah Khan <shuah@...nel.org>,
 Willem de Bruijn <willemdebruijn.kernel@...il.com>, sdf@...ichev.me,
 petrm@...dia.com, razor@...ckwall.org, idosch@...dia.com
Subject: Re: [PATCH v3 net-next 01/10] net: introduce mangleid_features

On 1/14/26 7:07 PM, Eric Dumazet wrote:
>> diff --git a/net/core/dev.c b/net/core/dev.c
>> index c711da335510..6154f306ed76 100644
>> --- a/net/core/dev.c
>> +++ b/net/core/dev.c
>> @@ -3788,8 +3788,10 @@ static netdev_features_t gso_features_check(const struct sk_buff *skb,
>>                 struct iphdr *iph = skb->encapsulation ?
>>                                     inner_ip_hdr(skb) : ip_hdr(skb);
>>
>> -               if (!(iph->frag_off & htons(IP_DF)))
>> +               if (!(iph->frag_off & htons(IP_DF))) {
>>                         features &= ~NETIF_F_TSO_MANGLEID;
> 
> Nit : We could avoid the above line, if we always make sure
> NETIF_F_TSO_MANGLEID is set in dev->mangleid_features

I thinks it makes a lot of sense. register_netdevice() could ensure such
 this constraint is respected; I'll add the following in the next
iteration and I will update the chunk here accordingly.

Thanks!

Paolo
---
diff --git a/net/core/dev.c b/net/core/dev.c
index c711da335510..a028ef1a3bcf 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -11372,6 +11372,12 @@ int register_netdevice(struct net_device *dev)
 	if (dev->hw_enc_features & NETIF_F_TSO)
 		dev->hw_enc_features |= NETIF_F_TSO_MANGLEID;

+	/* Any mangleid feature disables TSO_MANGLEID; including the latter
+	 * in mangleid_features allows for better code in the fastpath.
+	 */
+	if (dev->mangleid_features)
+		dev->mangleid_features |= NETIF_F_TSO_MANGLEID;
+
 	/* Make NETIF_F_HIGHDMA inheritable to VLAN devices.
 	 */
 	dev->vlan_features |= NETIF_F_HIGHDMA;