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Commit f6d460cf authored by David S. Miller's avatar David S. Miller
Browse files

ipv4: Make icmp route lookup code a bit clearer. 



The route lookup code in icmp_send() is slightly tricky as a result of
having to handle all of the requirements of RFC 4301 host relookups.

Pull the route resolution into a seperate function, so that the error
handling and route reference counting is hopefully easier to see and
contained wholly within this new routine.

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 2774c131

net/ipv4/icmp.c

+96 −79
Original line number Diff line number Diff line
@@ -369,6 +369,98 @@ static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb) 
	icmp_xmit_unlock(sk);

}



static struct rtable *icmp_route_lookup(struct net *net, struct sk_buff *skb_in,

					struct iphdr *iph,

					__be32 saddr, u8 tos,

					int type, int code,

					struct icmp_bxm *param)

{

	struct flowi fl = {

		.fl4_dst = (param->replyopts.srr ?

			    param->replyopts.faddr : iph->saddr),

		.fl4_src = saddr,

		.fl4_tos = RT_TOS(tos),

		.proto = IPPROTO_ICMP,

		.fl_icmp_type = type,

		.fl_icmp_code = code,

	};

	struct rtable *rt, *rt2;

	int err;



	security_skb_classify_flow(skb_in, &fl);

	err = __ip_route_output_key(net, &rt, &fl);

	if (err)

		return ERR_PTR(err);



	/* No need to clone since we're just using its address. */

	rt2 = rt;



	if (!fl.fl4_src)

		fl.fl4_src = rt->rt_src;



	err = xfrm_lookup(net, (struct dst_entry **)&rt, &fl, NULL, 0);

	switch (err) {

	case 0:

		if (rt != rt2)

			return rt;

		break;

	case -EPERM:

		rt = NULL;

		break;

	default:

		return ERR_PTR(err);

	}



	err = xfrm_decode_session_reverse(skb_in, &fl, AF_INET);

	if (err)

		goto relookup_failed;



	if (inet_addr_type(net, fl.fl4_src) == RTN_LOCAL) {

		err = __ip_route_output_key(net, &rt2, &fl);

	} else {

		struct flowi fl2 = {};

		unsigned long orefdst;



		fl2.fl4_dst = fl.fl4_src;

		err = ip_route_output_key(net, &rt2, &fl2);

		if (err)

			goto relookup_failed;

		/* Ugh! */

		orefdst = skb_in->_skb_refdst; /* save old refdst */

		err = ip_route_input(skb_in, fl.fl4_dst, fl.fl4_src,

				     RT_TOS(tos), rt2->dst.dev);



		dst_release(&rt2->dst);

		rt2 = skb_rtable(skb_in);

		skb_in->_skb_refdst = orefdst; /* restore old refdst */

	}



	if (err)

		goto relookup_failed;



	err = xfrm_lookup(net, (struct dst_entry **)&rt2, &fl, NULL,

			  XFRM_LOOKUP_ICMP);

	switch (err) {

	case 0:

		dst_release(&rt->dst);

		rt = rt2;

		break;

	case -EPERM:

		return ERR_PTR(err);

	default:

		if (!rt)

			return ERR_PTR(err);

		break;

	}





	return rt;



relookup_failed:

	if (rt)

		return rt;

	return ERR_PTR(err);

}



/*

 *	Send an ICMP message in response to a situation
@@ -506,86 +598,11 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info) 
	ipc.opt = &icmp_param.replyopts;

	ipc.tx_flags = 0;



	{

		struct flowi fl = {

			.fl4_dst = icmp_param.replyopts.srr ?

				   icmp_param.replyopts.faddr : iph->saddr,

			.fl4_src = saddr,

			.fl4_tos = RT_TOS(tos),

			.proto = IPPROTO_ICMP,

			.fl_icmp_type = type,

			.fl_icmp_code = code,

		};

		int err;

		struct rtable *rt2;



		security_skb_classify_flow(skb_in, &fl);

		if (__ip_route_output_key(net, &rt, &fl))

			goto out_unlock;



		/* No need to clone since we're just using its address. */

		rt2 = rt;



		if (!fl.nl_u.ip4_u.saddr)

			fl.nl_u.ip4_u.saddr = rt->rt_src;



		err = xfrm_lookup(net, (struct dst_entry **)&rt, &fl, NULL, 0);

		switch (err) {

		case 0:

			if (rt != rt2)

				goto route_done;

			break;

		case -EPERM:

			rt = NULL;

			break;

		default:

	rt = icmp_route_lookup(net, skb_in, iph, saddr, tos,

			       type, code, &icmp_param);

	if (IS_ERR(rt))

		goto out_unlock;

		}



		if (xfrm_decode_session_reverse(skb_in, &fl, AF_INET))

			goto relookup_failed;



		if (inet_addr_type(net, fl.fl4_src) == RTN_LOCAL)

			err = __ip_route_output_key(net, &rt2, &fl);

		else {

			struct flowi fl2 = {};

			unsigned long orefdst;



			fl2.fl4_dst = fl.fl4_src;

			if (ip_route_output_key(net, &rt2, &fl2))

				goto relookup_failed;



			/* Ugh! */

			orefdst = skb_in->_skb_refdst; /* save old refdst */

			err = ip_route_input(skb_in, fl.fl4_dst, fl.fl4_src,

					     RT_TOS(tos), rt2->dst.dev);



			dst_release(&rt2->dst);

			rt2 = skb_rtable(skb_in);

			skb_in->_skb_refdst = orefdst; /* restore old refdst */

		}



		if (err)

			goto relookup_failed;



		err = xfrm_lookup(net, (struct dst_entry **)&rt2, &fl, NULL,

				  XFRM_LOOKUP_ICMP);

		switch (err) {

		case 0:

			dst_release(&rt->dst);

			rt = rt2;

			break;

		case -EPERM:

			goto ende;

		default:

relookup_failed:

			if (!rt)

				goto out_unlock;

			break;

		}

	}



route_done:

	if (!icmpv4_xrlim_allow(net, rt, type, code))

		goto ende;