[SLOF] [PATCH 5/5] ipv6: Replace magic number 1500 with ETH_MTU_SIZE (i.e. 1518)

[Andrew Jones]

On Mon, May 02, 2016 at 09:55:31PM +0200, Thomas Huth wrote:
> The whole ethernet frame can be up to 1518 bytes including the ethernet
> header. So this value should be used instead of 1500 when the whole
> ethernet packet is affected. Since we've already got a nice define
> for this value, use ETH_MTU_SIZE where it is appropriate.
> 
> This patch also removes a "memset(n->eth_frame, 0, 1500)" in send_ipv6()
> to get rid of the magic value 1500 there -- it can be removed since
> the whole ethernet packet is filled into the buffer right after the
> memset, so there are no gaps that should be cleared first.
> 
> Signed-off-by: Thomas Huth <thuth at redhat.com>
> ---
>  clients/net-snk/app/netlib/ipv6.c | 3 +--
>  clients/net-snk/app/netlib/ndp.h  | 2 +-
>  2 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/clients/net-snk/app/netlib/ipv6.c b/clients/net-snk/app/netlib/ipv6.c
> index 6aa1ea3..300c913 100644
> --- a/clients/net-snk/app/netlib/ipv6.c
> +++ b/clients/net-snk/app/netlib/ipv6.c
> @@ -501,7 +501,7 @@ int send_ipv6(int fd, void* buffer, int len)
>  
>  	memcpy(&ip_dst, &ip6h->dst, 16);
>  
> -	if(len + sizeof(struct ethhdr) > 1500)
> +	if(len + sizeof(struct ethhdr) > ETH_MTU_SIZE)
>  		return -1;
>  
>  	if ( ip6_cmp (&ip6h->src, &null_ip6))
> @@ -553,7 +553,6 @@ int send_ipv6(int fd, void* buffer, int len)
>  				send_neighbour_solicitation (fd, &ip_dst);
>  
>  				// Store the packet until we know the MAC address
> -				memset(n->eth_frame, 0, 1500);
>  				fill_ethhdr (n->eth_frame,
>  					     htons(ETHERTYPE_IPv6),
>  					     get_mac_address(),
> diff --git a/clients/net-snk/app/netlib/ndp.h b/clients/net-snk/app/netlib/ndp.h
> index 74fbd8b..7274f10 100644
> --- a/clients/net-snk/app/netlib/ndp.h
> +++ b/clients/net-snk/app/netlib/ndp.h
> @@ -48,7 +48,7 @@ struct neighbor {
>  	uint8_t times_asked;
>  	/* ... */
>  	struct neighbor *next;
> -	uint8_t eth_frame[1500]; //FIXME

I did a git-blame to try and figure out what this FIXME was indicating
needed fixing, but the patch it came from was a monolithic add-
everything patch. Was there a desire to separate the frame from the
neighbor struct?

> +	uint8_t eth_frame[ETH_MTU_SIZE];
>  	uint32_t eth_len;
>  
>  #define NB_INCOMPLETE 1
> -- 
> 1.8.3.1
> 

Reviewed-by: Andrew Jones <drjones at redhat.com>