netdev - Re: [PATCH 2/2] be2net: drop non-tso frames longer than mtu

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Message-ID: <1381844840.2045.37.camel@edumazet-glaptop.roam.corp.google.com>
Date:	Tue, 15 Oct 2013 06:47:20 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Sathya Perla <sathya.perla@...lex.com>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] be2net: drop non-tso frames longer than mtu

On Tue, 2013-10-15 at 17:26 +0530, Sathya Perla wrote:
> From: Vasundhara Volam <vasundhara.volam@...lex.com>
> 
> Pktgen can generate non-TSO frames of arbitrary length disregarding
> the MTU value of the physical interface. Drop such frames in the driver
> instead of sending them to HW as it cannot handle such frames.
> 
> Signed-off-by: Vasundhara Volam <vasundhara.volam@...lex.com>
> Signed-off-by: Sathya Perla <sathya.perla@...lex.com>
> ---
>  drivers/net/ethernet/emulex/benet/be_main.c |    9 +++++++--
>  1 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/emulex/benet/be_main.c b/drivers/net/ethernet/emulex/benet/be_main.c
> index 2c38cc4..76057b8 100644
> --- a/drivers/net/ethernet/emulex/benet/be_main.c
> +++ b/drivers/net/ethernet/emulex/benet/be_main.c
> @@ -855,6 +855,13 @@ static struct sk_buff *be_xmit_workarounds(struct be_adapter *adapter,
>  	unsigned int eth_hdr_len;
>  	struct iphdr *ip;
>  
> +	/* Don't allow non-TSO packets longer than MTU */
> +	eth_hdr_len = (ntohs(skb->protocol) == ETH_P_8021Q) ?
> +			VLAN_ETH_HLEN : ETH_HLEN;
> +	if (!skb_is_gso(skb) &&
> +	    (skb->len - eth_hdr_len) > adapter->netdev->mtu)
> +			goto tx_drop;
> +

When you say 'cannot handle them', is it some kind of nasty thing like
hang / crash ?

One could imagine gso_size + sizeof(headers) > mtu, and give the same
problem ?


AFAIK, we have no check in net/core/dev.c.

Maybe we should instead add them there (and in pktgen)



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