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Commit a3c00e46 authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by David S. Miller
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ipv6: Remove BACKTRACK macro 



It is the prep work to reduce the number of calls to fib6_lookup().

The BACKTRACK macro could be hard-to-read and error-prone due to
its side effects (mainly goto).

This patch is to:
1. Replace BACKTRACK macro with a function (fib6_backtrack) with the following
   return values:
   * If it is backtrack-able, returns next fn for retry.
   * If it reaches the root, returns NULL.
2. The caller needs to decide if a backtrack is needed (by testing
   rt == net->ipv6.ip6_null_entry).
3. Rename the goto labels in ip6_pol_route() to make the next few
   patches easier to read.

Cc: David Miller <davem@davemloft.net>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 105970f6

net/ipv6/route.c

+40 −30
Original line number Diff line number Diff line
@@ -772,23 +772,22 @@ int rt6_route_rcv(struct net_device *dev, u8 *opt, int len, 
}

#endif



#define BACKTRACK(__net, saddr)			\

do { \

	if (rt == __net->ipv6.ip6_null_entry) {	\

		struct fib6_node *pn; \

		while (1) { \

			if (fn->fn_flags & RTN_TL_ROOT) \

				goto out; \

			pn = fn->parent; \

			if (FIB6_SUBTREE(pn) && FIB6_SUBTREE(pn) != fn) \

				fn = fib6_lookup(FIB6_SUBTREE(pn), NULL, saddr); \

			else \

				fn = pn; \

			if (fn->fn_flags & RTN_RTINFO) \

				goto restart; \

		} \

	} \

} while (0)

static struct fib6_node* fib6_backtrack(struct fib6_node *fn,

					struct in6_addr *saddr)

{

	struct fib6_node *pn;

	while (1) {

		if (fn->fn_flags & RTN_TL_ROOT)

			return NULL;

		pn = fn->parent;

		if (FIB6_SUBTREE(pn) && FIB6_SUBTREE(pn) != fn)

			fn = fib6_lookup(FIB6_SUBTREE(pn), NULL, saddr);

		else

			fn = pn;

		if (fn->fn_flags & RTN_RTINFO)

			return fn;

	}

}



static struct rt6_info *ip6_pol_route_lookup(struct net *net,

					     struct fib6_table *table,
@@ -804,8 +803,11 @@ static struct rt6_info *ip6_pol_route_lookup(struct net *net, 
	rt = rt6_device_match(net, rt, &fl6->saddr, fl6->flowi6_oif, flags);

	if (rt->rt6i_nsiblings && fl6->flowi6_oif == 0)

		rt = rt6_multipath_select(rt, fl6, fl6->flowi6_oif, flags);

	BACKTRACK(net, &fl6->saddr);

out:

	if (rt == net->ipv6.ip6_null_entry) {

		fn = fib6_backtrack(fn, &fl6->saddr);

		if (fn)

			goto restart;

	}

	dst_use(&rt->dst, jiffies);

	read_unlock_bh(&table->tb6_lock);

	return rt;
@@ -924,19 +926,25 @@ static struct rt6_info *ip6_pol_route(struct net *net, struct fib6_table *table, 


	strict |= flags & RT6_LOOKUP_F_IFACE;



relookup:

redo_fib6_lookup_lock:

	read_lock_bh(&table->tb6_lock);



restart_2:

redo_fib6_lookup:

	fn = fib6_lookup(&table->tb6_root, &fl6->daddr, &fl6->saddr);



restart:

redo_rt6_select:

	rt = rt6_select(fn, oif, strict | reachable);

	if (rt->rt6i_nsiblings)

		rt = rt6_multipath_select(rt, fl6, oif, strict | reachable);

	BACKTRACK(net, &fl6->saddr);

	if (rt == net->ipv6.ip6_null_entry ||

	    rt->rt6i_flags & RTF_CACHE)

	if (rt == net->ipv6.ip6_null_entry) {

		fn = fib6_backtrack(fn, &fl6->saddr);

		if (fn)

			goto redo_rt6_select;

		else

			goto out;

	}



	if (rt->rt6i_flags & RTF_CACHE)

		goto out;



	dst_hold(&rt->dst);
@@ -967,12 +975,12 @@ static struct rt6_info *ip6_pol_route(struct net *net, struct fib6_table *table, 
	 * released someone could insert this route.  Relookup.

	 */

	ip6_rt_put(rt);

	goto relookup;

	goto redo_fib6_lookup_lock;



out:

	if (reachable) {

		reachable = 0;

		goto restart_2;

		goto redo_fib6_lookup;

	}

	dst_hold(&rt->dst);

	read_unlock_bh(&table->tb6_lock);
@@ -1235,10 +1243,12 @@ static struct rt6_info *__ip6_route_redirect(struct net *net, 
		rt = net->ipv6.ip6_null_entry;

	else if (rt->dst.error) {

		rt = net->ipv6.ip6_null_entry;

		goto out;

	} else if (rt == net->ipv6.ip6_null_entry) {

		fn = fib6_backtrack(fn, &fl6->saddr);

		if (fn)

			goto restart;

	}

	BACKTRACK(net, &fl6->saddr);

out:



	dst_hold(&rt->dst);



	read_unlock_bh(&table->tb6_lock);