Subject: Re: [PATCH] netlink: add NETLINK_BROADCAST_ERROR socket option

From: Patrick McHardy <[email-masked]>
Date: Tue, 17 Feb 2009 15:18:46 +0100

Pablo Neira Ayuso wrote:
> @@ -973,7 +974,7 @@ static inline int do_one_broadcast(struct sock *sk,
>  	if (!net_eq(sock_net(sk), p->net))
>  		goto out;
>  
> -	if (p->failure) {
> +	if ((nlk->flags & NETLINK_BROADCAST_SEND_ERROR) && p->failure) {
>  		netlink_overrun(sk);
>  		goto out;
>  	}
 >
> @@ -994,13 +995,15 @@ static inline int do_one_broadcast(struct sock *sk,
>  	if (p->skb2 == NULL) {
>  		netlink_overrun(sk);
>  		/* Clone failed. Notify ALL listeners. */
> -		p->failure = 1;
> +		if (nlk->flags & NETLINK_BROADCAST_SEND_ERROR)
> +			p->failure = 1;

Almost :) If we didn't manage to clone, we can't deliver to *any*
socket, so the check in the first chunk above is incorrect. It
needs to always call netlink_overrun(), additionally it needs to
set delivery_failure when the SEND_ERROR flag is present.

Something like this:

  	if (p->failure) {
  +		if (nlk->flags & NETLINK_BROADCAST_SEND_ERROR)
  +			p->delivery_failure = 1;
   		netlink_overrun(sk);
   		goto out;
   	}

>  	} else if (sk_filter(sk, p->skb2)) {
>  		kfree_skb(p->skb2);
>  		p->skb2 = NULL;
>  	} else if ((val = netlink_broadcast_deliver(sk, p->skb2)) < 0) {
>  		netlink_overrun(sk);
> -		p->delivery_failure = 1;
> +		if (nlk->flags & NETLINK_BROADCAST_SEND_ERROR)
> +			p->delivery_failure = 1;
>  	} else {
>  		p->congested |= val;
>  		p->delivered = 1;