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net: introduce mangleid_features

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Some/most devices implementing gso_partial need to disable the GSO partial
features when the IP ID can't be mangled; to that extend each of them
implements something alike the following[1]:

	if (skb->encapsulation && !(features & NETIF_F_TSO_MANGLEID))
		features &= ~NETIF_F_TSO;

in the ndo_features_check() op, which leads to a bit of duplicate code.

Later patch in the series will implement GSO partial support for virtual
devices, and the current status quo will require more duplicate code and
a new indirect call in the TX path for them.

Introduce the mangleid_features mask, allowing the core to disable NIC
features based on/requiring MANGLEID, without any further intervention
from the driver.

The same functionality could be alternatively implemented adding a single
boolean flag to the struct net_device, but would require an additional
checks in ndo_features_check().

Also note that [1] is incorrect if the NIC additionally implements
NETIF_F_GSO_UDP_L4, mangleid_features transparently handle even such a
case.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/5a7cdaeea40b0a29b88e525b6c942d73ed3b8ce7.1769011015.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Paolo Abeni 2026-01-21 17:11:27 +01:00 • committed by Jakub Kicinski
parent 8811df1dd4
commit 31c5a71d98
2 changed files with 7 additions and 1 deletions
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3
include/linux/netdevice.h
View file

@ -1831,6 +1831,8 @@ enum netdev_reg_state {
*
* @mpls_features: Mask of features inheritable by MPLS
* @gso_partial_features: value(s) from NETIF_F_GSO\*
* @mangleid_features: Mask of features requiring MANGLEID, will be
* disabled together with the latter.
*
* @ifindex: interface index
* @group: The group the device belongs to
@ -2219,6 +2221,7 @@ struct net_device {
netdev_features_t vlan_features;
netdev_features_t hw_enc_features;
netdev_features_t mpls_features;
netdev_features_t mangleid_features;
unsigned int min_mtu;
unsigned int max_mtu;

5
net/core/dev.c
View file

@ -3802,7 +3802,7 @@ static netdev_features_t gso_features_check(const struct sk_buff *skb,
inner_ip_hdr(skb) : ip_hdr(skb);
if (!(iph->frag_off & htons(IP_DF)))
features &= ~NETIF_F_TSO_MANGLEID;
features &= ~dev->mangleid_features;
}
/* NETIF_F_IPV6_CSUM does not support IPv6 extension headers,
@ -11402,6 +11402,9 @@ int register_netdevice(struct net_device *dev)
if (dev->hw_enc_features & NETIF_F_TSO)
dev->hw_enc_features |= NETIF_F_TSO_MANGLEID;
/* TSO_MANGLEID belongs in mangleid_features by definition */
dev->mangleid_features |= NETIF_F_TSO_MANGLEID;
/* Make NETIF_F_HIGHDMA inheritable to VLAN devices.
*/
dev->vlan_features |= NETIF_F_HIGHDMA;