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Transforming code to using ICMP packet accessors

DISCUSSION David Howells 2 participants 3 messages Apr 26, 2007

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#0 lore raw

How do I convert:

	addr = *(__be32 *)(skb->nh.raw + serr->addr_offset);

to use the ICMP accessor macros now that skb->nh is no longer available? I was using this to pluck an address out of the ICMP packet payload, but

	void rxrpc_UDP_error_report(struct sock *sk)
	{
		struct sock_exterr_skb *serr;
	...
		struct sk_buff *skb;
		__be32 addr;
		__be16 port;
	...

		skb = skb_dequeue(&sk->sk_error_queue);
		if (!skb) {
			_leave("UDP socket errqueue empty");
			return;
		}
	...

		serr = SKB_EXT_ERR(skb);
		addr = *(__be32 *)(skb->nh.raw + serr->addr_offset);
		port = serr->port;

		_net("Rx UDP Error from "NIPQUAD_FMT":%hu",
		     NIPQUAD(addr), ntohs(port));
	...
	}

Should I do this?:

	addr = *(__be32 *)(skb_network_header(skb) + serr->addr_offset);

David

#1 lore raw
Quoted 33 lines · David Howells

How do I convert:

        addr = *(__be32 *)(skb->nh.raw + serr->addr_offset);

to use the ICMP accessor macros now that skb->nh is no longer available? I was using this to pluck an address out of the ICMP packet payload, but

        void rxrpc_UDP_error_report(struct sock *sk)
        {
                struct sock_exterr_skb *serr;
        ...
                struct sk_buff *skb;
                __be32 addr;
                __be16 port;
        ...

                skb = skb_dequeue(&sk->sk_error_queue);
                if (!skb) {
                        _leave("UDP socket errqueue empty");
                        return;
                }
        ...

                serr = SKB_EXT_ERR(skb);
                addr = *(__be32 *)(skb->nh.raw + serr->addr_offset);
                port = serr->port;

                _net("Rx UDP Error from "NIPQUAD_FMT":%hu",
                     NIPQUAD(addr), ntohs(port));
        ...
        }
Quoted 3 lines

Should I do this?:

        addr = *(__be32 *)(skb_network_header(skb) + serr->addr_offset);

Yes, as this is the only use in this function.

When there is more than one use, create a pointer from skb_network_header(skb). That way the skb->head + skb->network_header math is done just once.

- Arnaldo

#2 lore raw
Quoted 1 line · Arnaldo Carvalho de Melo

Yes, as this is the only use in this function.

Thanks!

David