On Mon, 12 Mar 2018 23:42:48 +0100
Rafał Miłecki <zajec5@xxxxxxxxx> wrote:
> 2) Blame bridge + mcast-to-ucast + hairpin for 802.11f incompatibility
>
> If we agree that 802.11f support in FullMAC firmware is acceptable, then
> we have to make sure Linux's bridge doesn't break it by passing 802.11f
> (broadcast) frames back to the source interface. That would require a
> check like in below diff + proper code for handling such packets. I'm
> afraid I'm not familiar with bridge code enough to complete that.
>
> diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
> index edae702..9e5d6ea 100644
> --- a/net/bridge/br_input.c
> +++ b/net/bridge/br_input.c
> @@ -126,6 +126,27 @@ static void br_do_proxy_arp(struct sk_buff *skb, struct net_bridge *br,
> }
> }
>
> +static bool br_skb_is_iapp_add_packet(struct sk_buff *skb)
> +{
> + const u8 iapp_add_packet[6] __aligned(2) = {
> + 0x00, 0x01, 0xaf, 0x81, 0x01, 0x00,
> + };
> +#if !defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
> + const u16 *a = (const u16 *)skb->data;
> + const u16 *b = (const u16 *)iapp_add_packet;
> +#endif
> +
> + if (skb->len != 6)
> + return false;
> +
> +#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
> + return !(((*(const u32 *)skb->data) ^ (*(const u32 *)iapp_add_packet)) |
> + ((*(const u16 *)(skb->data + 4)) ^ (*(const u16 *)(iapp_add_packet + 4))));
> +#else
> + return !((a[0] ^ b[0]) | (a[1] ^ b[1]) | (a[2] ^ b[2]));
> +#endif
> +}
> +
> /* note: already called with rcu_read_lock */
> int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
> {
> @@ -155,6 +176,8 @@ int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb
> if (is_multicast_ether_addr(dest)) {
> /* by definition the broadcast is also a multicast address */
> if (is_broadcast_ether_addr(dest)) {
> + if (br_skb_is_iapp_add_packet(skb))
> + pr_warn("This packet should not be passed back to the source interface!\n");
> pkt_type = BR_PKT_BROADCAST;
> local_rcv = true;
> } else {
Don't like bridge doing special case code for magic received values directly in input path.
Really needs to be generic which is why I suggested ebtables.
