netdev - Re: [PATCH net-next v1] net: gso: Add GSO support for NSH (Network Service Header)

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Date:   Thu, 24 Aug 2017 16:13:26 +0200
From:   Jiri Benc <jbenc@...hat.com>
To:     Yi Yang <yi.y.yang@...el.com>
Cc:     netdev@...r.kernel.org, simon.horman@...ronome.com
Subject: Re: [PATCH net-next v1] net: gso: Add GSO support for NSH (Network
 Service Header)

On Thu, 24 Aug 2017 17:36:16 +0800, Yi Yang wrote:
>  include/net/nsh.h             | 307 ++++++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/if_ether.h |   1 +
>  net/Kconfig                   |   1 +
>  net/Makefile                  |   1 +
>  net/nsh/Kconfig               |  10 ++
>  net/nsh/Makefile              |   4 +
>  net/nsh/nsh_gso.c             | 116 ++++++++++++++++

Please consider making this a patchset, with a patch adding the NSH
structures and helper functions, a patch adding GSO and a patch adding
OVS support. That way, everything can be reviewed together, yet the
patches are reasonably contained.

> +config NET_NSH_GSO
> +	bool "NSH GSO support"
> +	depends on INET
> +	default y
> +	---help---
> +	 This allows segmentation of GSO packet that have had NSH header pushed         onto them and thus become NSH GSO packets.

Seems you're missing a newline here.

> +static struct sk_buff *nsh_gso_segment(struct sk_buff *skb,
> +				       netdev_features_t features)
> +{
> +	struct sk_buff *segs = ERR_PTR(-EINVAL);
> +	__be16 protocol = skb->protocol;
> +	__be16 inner_proto;
> +	u16 mac_offset = skb->mac_header;
> +	u16 mac_len = skb->mac_len;
> +	struct nsh_hdr *nsh;
> +	unsigned int nsh_hlen;
> +	const struct net_offload *ops;
> +	struct sk_buff *(*gso_inner_segment)(struct sk_buff *skb,
> +					     netdev_features_t features);
> +
> +	skb_reset_network_header(skb);
> +	nsh = (struct nsh_hdr *)skb_network_header(skb);
> +	nsh_hlen = nsh_hdr_len(nsh);
> +	if (unlikely(!pskb_may_pull(skb, nsh_hlen)))
> +		goto out;

You have to reload nsh after this.

> +
> +	__skb_pull(skb, nsh_hlen);
> +
> +	skb_reset_mac_header(skb);
> +	skb_reset_mac_len(skb);
> +
> +	rcu_read_lock();
> +	switch (nsh->next_proto) {
> +	case NSH_P_ETHERNET:
> +		inner_proto = htons(ETH_P_TEB);
> +		gso_inner_segment = skb_mac_gso_segment;
> +		break;
> +	case NSH_P_IPV4:
> +		inner_proto = htons(ETH_P_IP);
> +		ops = rcu_dereference(inet_offloads[inner_proto]);
> +		if (!ops || !ops->callbacks.gso_segment)
> +			goto out;
> +		gso_inner_segment = ops->callbacks.gso_segment;
> +		break;
> +	case NSH_P_IPV6:
> +		inner_proto = htons(ETH_P_IPV6);
> +		ops = rcu_dereference(inet6_offloads[inner_proto]);
> +		if (!ops || !ops->callbacks.gso_segment)
> +			goto out;
> +		gso_inner_segment = ops->callbacks.gso_segment;
> +		break;
> +	case NSH_P_NSH:
> +		inner_proto = htons(ETH_P_NSH);
> +		gso_inner_segment = nsh_gso_segment;

This doesn't look correct. Recursive call to nsh_gso_segment will reset
mac header, causing skb_segment not to copy the previous NSH header(s)
to the new segments.

> +		break;
> +	default:
> +		skb_gso_error_unwind(skb, protocol, nsh_hlen, mac_offset,
> +				     mac_len);
> +		goto out;
> +	}
> +
> +	skb->protocol = inner_proto;
> +	segs = gso_inner_segment(skb, features);
> +	if (IS_ERR_OR_NULL(segs)) {
> +		skb_gso_error_unwind(skb, protocol, nsh_hlen, mac_offset,
> +				     mac_len);
> +		goto out;
> +	}
> +
> +	do {
> +		skb->mac_len = mac_len;
> +		skb->protocol = protocol;
> +
> +		skb_reset_inner_network_header(skb);

This looks superfluous.

> +
> +		__skb_push(skb, nsh_hlen);
> +
> +		skb_reset_mac_header(skb);
> +		skb_set_network_header(skb, mac_len);
> +	} while ((skb = skb->next));
> +
> +out:
> +	rcu_read_unlock();
> +	return segs;
> +}
> +
> +static struct packet_offload nsh_offload __read_mostly = {
> +	.type = cpu_to_be16(ETH_P_NSH),
> +	.priority = 15,
> +	.callbacks = {
> +		.gso_segment    =	nsh_gso_segment,
> +	},
> +};
> +
> +static int __init nsh_gso_init(void)
> +{
> +	dev_add_offload(&nsh_offload);
> +
> +	return 0;
> +}
> +
> +fs_initcall(nsh_gso_init);

device_initcall should be enough. I doubt we'll be doing NFS over
NSH ;-)

 Jiri