Subject: Re: [PATCH net-next] xen-netback: Fix pull size in checksum_setup_ip*

From: Zoltan Kiss <[email-masked]>
Date: Fri, 29 Nov 2013 20:26:15 +0000

Or would it make sense to drop header_size and use off + something as 
function parameters?

Zoli

On 29/11/13 18:56, Zoltan Kiss wrote:
> Before checksum setup we need to make sure we have enough data in linear
> buffer, so we do a pull if not. The calculation of the required data counts
> with skb->network_header, which is the headroom size actually. This is not
> necessary, and can cause unreasonable pulling. I've also removed
> MAX_IPOPTLEN, as we only need the base header at that point.
>
> Signed-off-by: Zoltan Kiss <[email-masked]>
>
> ---
>   drivers/net/xen-netback/netback.c |   24 ++++++++----------------
>   1 file changed, 8 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
> index 919b650..adadf76 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -1169,8 +1169,7 @@ static int checksum_setup_ip(struct xenvif *vif, struct sk_buff *skb,
>
>   	off = sizeof(struct iphdr);
>
> -	header_size = skb->network_header + off + MAX_IPOPTLEN;
> -	maybe_pull_tail(skb, header_size);
> +	maybe_pull_tail(skb, off);
>
>   	off = iph->ihl * 4;
>
> @@ -1183,8 +1182,7 @@ static int checksum_setup_ip(struct xenvif *vif, struct sk_buff *skb,
>   		if (recalculate_partial_csum) {
>   			struct tcphdr *tcph = tcp_hdr(skb);
>
> -			header_size = skb->network_header +
> -				off +
> +			header_size = off +
>   				sizeof(struct tcphdr);
>   			maybe_pull_tail(skb, header_size);
>
> @@ -1201,8 +1199,7 @@ static int checksum_setup_ip(struct xenvif *vif, struct sk_buff *skb,
>   		if (recalculate_partial_csum) {
>   			struct udphdr *udph = udp_hdr(skb);
>
> -			header_size = skb->network_header +
> -				off +
> +			header_size = off +
>   				sizeof(struct udphdr);
>   			maybe_pull_tail(skb, header_size);
>
> @@ -1241,8 +1238,7 @@ static int checksum_setup_ipv6(struct xenvif *vif, struct sk_buff *skb,
>
>   	off = sizeof(struct ipv6hdr);
>
> -	header_size = skb->network_header + off;
> -	maybe_pull_tail(skb, header_size);
> +	maybe_pull_tail(skb, off);
>
>   	nexthdr = ipv6h->nexthdr;
>
> @@ -1254,8 +1250,7 @@ static int checksum_setup_ipv6(struct xenvif *vif, struct sk_buff *skb,
>   		case IPPROTO_ROUTING: {
>   			struct ipv6_opt_hdr *hp = (void *)(skb->data + off);
>
> -			header_size = skb->network_header +
> -				off +
> +			header_size = off +
>   				sizeof(struct ipv6_opt_hdr);
>   			maybe_pull_tail(skb, header_size);
>
> @@ -1266,8 +1261,7 @@ static int checksum_setup_ipv6(struct xenvif *vif, struct sk_buff *skb,
>   		case IPPROTO_AH: {
>   			struct ip_auth_hdr *hp = (void *)(skb->data + off);
>
> -			header_size = skb->network_header +
> -				off +
> +			header_size = off +
>   				sizeof(struct ip_auth_hdr);
>   			maybe_pull_tail(skb, header_size);
>
> @@ -1305,8 +1299,7 @@ static int checksum_setup_ipv6(struct xenvif *vif, struct sk_buff *skb,
>   		if (recalculate_partial_csum) {
>   			struct tcphdr *tcph = tcp_hdr(skb);
>
> -			header_size = skb->network_header +
> -				off +
> +			header_size = off +
>   				sizeof(struct tcphdr);
>   			maybe_pull_tail(skb, header_size);
>
> @@ -1324,8 +1317,7 @@ static int checksum_setup_ipv6(struct xenvif *vif, struct sk_buff *skb,
>   		if (recalculate_partial_csum) {
>   			struct udphdr *udph = udp_hdr(skb);
>
> -			header_size = skb->network_header +
> -				off +
> +			header_size = off +
>   				sizeof(struct udphdr);
>   			maybe_pull_tail(skb, header_size);
>
>