Subject: Re: [PATCH v2 net-next] Enhanced skb_mpls_pop to update ethertype of the packet in all the cases when an ethernet header is present is the packet.

From: Jakub Kicinski <[email-masked]>
Date: Sun, 24 Nov 2019 19:10:08 -0800

On Sat, 23 Nov 2019 16:04:59 +0530, Martin Varghese wrote:
> From: Martin Varghese <[email-masked]>
> 
> The skb_mpls_pop was not updating ethertype of an ethernet packet if the
> packet was originally received from a non ARPHRD_ETHER device.
> 
> In the below OVS data path flow, since the device corresponding to port 7
> is an l3 device (ARPHRD_NONE) the skb_mpls_pop function does not update
> the ethertype of the packet even though the previous push_eth action had
> added an ethernet header to the packet.
> 
> recirc_id(0),in_port(7),eth_type(0x8847),
> mpls(label=12/0xfffff,tc=0/0,ttl=0/0x0,bos=1/1),
> actions:push_eth(src=00:00:00:00:00:00,dst=00:00:00:00:00:00),
> pop_mpls(eth_type=0x800),4
> 
> Signed-off-by: Martin Varghese <[email-masked]>

So this fixes all the way back to commit ed246cee09b9 ("net: core: move
pop MPLS functionality from OvS to core helper")? Please add a Fixes: tag.

> Changes in v2:
>     - check for dev type removed while updating ethertype
>       in function skb_mpls_pop.
>     - key->mac_proto is checked in function pop_mpls to pass
>       ethernt flag to skb_mpls_pop.
>     - dev type is checked in function tcf_mpls_act to pass
>       ethernet flag to skb_mpls_pop.

nit: changelog can be kept in the commit message for netdev patches

> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 867e61d..988eefb 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -5529,12 +5529,13 @@ int skb_mpls_push(struct sk_buff *skb, __be32 mpls_lse, __be16 mpls_proto,
>   * @skb: buffer
>   * @next_proto: ethertype of header after popped MPLS header
>   * @mac_len: length of the MAC header
> - *
> + * @ethernet: flag to indicate if ethernet header is present in packet

Please don't remove the empty line between params and function
description.

>   * Expects skb->data at mac header.
>   *
>   * Returns 0 on success, -errno otherwise.
>   */
> -int skb_mpls_pop(struct sk_buff *skb, __be16 next_proto, int mac_len)
> +int skb_mpls_pop(struct sk_buff *skb, __be16 next_proto, int mac_len,
> +		 bool ethernet)
>  {
>  	int err;
>  

> diff --git a/net/sched/act_mpls.c b/net/sched/act_mpls.c
> index 4d8c822..f919f95 100644
> --- a/net/sched/act_mpls.c
> +++ b/net/sched/act_mpls.c
> @@ -13,6 +13,7 @@
>  #include <net/pkt_sched.h>
>  #include <net/pkt_cls.h>
>  #include <net/tc_act/tc_mpls.h>
> +#include <linux/if_arp.h>

Please retain the alphabetical order of includes.

>  static unsigned int mpls_net_id;
>  static struct tc_action_ops act_mpls_ops;
> @@ -76,7 +77,8 @@ static int tcf_mpls_act(struct sk_buff *skb, const struct tc_action *a,
>  
>  	switch (p->tcfm_action) {
>  	case TCA_MPLS_ACT_POP:
> -		if (skb_mpls_pop(skb, p->tcfm_proto, mac_len))
> +		if (skb_mpls_pop(skb, p->tcfm_proto, mac_len,
> +				 (skb->dev && skb->dev->type == ARPHRD_ETHER)))

Parenthesis unnecessary

>  			goto drop;
>  		break;
>  	case TCA_MPLS_ACT_PUSH: