netdev - Re: [PATCH 2/2] net: ip, ipv6: handle gso skbs in forwarding path

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Message-ID: <1390846967.27806.75.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Mon, 27 Jan 2014 10:22:47 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Florian Westphal <fw@...len.de>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] net: ip, ipv6: handle gso skbs in forwarding path

On Mon, 2014-01-27 at 09:22 +0100, Florian Westphal wrote:

> +/* called if GSO skb needs to be fragmented on forward.  */
> +static int ip_forward_finish_gso(struct sk_buff *skb)
> +{
> +	netdev_features_t features = netif_skb_features(skb);
> +	struct sk_buff *segs;
> +	int ret = 0;
> +
> +	segs = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
> +	if (IS_ERR(segs)) {
> +		kfree_skb(skb);
> +		return -ENOMEM;
> +	}
> +
> +	consume_skb(skb);
> +
> +	do {
> +		struct sk_buff *nskb = segs->next;
> +		int err;
> +
> +		segs->next = NULL;
> +		err = dst_output(segs);
> +
> +		if (err && ret == 0)
> +			ret = err;
> +		segs = nskb;
> +	} while (segs);
> +
> +	return ret;
> +}
> +

Its still unclear if this is the best strategy.

TCP stream not using DF flag are very unlikely to care if we adjust
their MTU (lowering gso_size) at this point ?



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