netfilter: fix ebtables compat support

commit 255d0dc34068a976 (netfilter: x_table: speedup compat operations)
made ebtables not working anymore.

1) xt_compat_calc_jump() is not an exact match lookup
2) compat_table_info() has a typo in xt_compat_init_offsets() call
3) compat_do_replace() misses a xt_compat_init_offsets() call

Reported-by: dann frazier <dannf@dannf.org>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>

net/bridge/netfilter/ebtables.c

@@ -1766,7 +1766,7 @@ static int compat_table_info(const struct ebt_table_info *info,
 
 	newinfo->entries_size = size;
 
-	xt_compat_init_offsets(AF_INET, info->nentries);
+	xt_compat_init_offsets(NFPROTO_BRIDGE, info->nentries);
 	return EBT_ENTRY_ITERATE(entries, size, compat_calc_entry, info,
 							entries, newinfo);
 }
@@ -2240,6 +2240,7 @@ static int compat_do_replace(struct net *net, void __user *user,
 
 	xt_compat_lock(NFPROTO_BRIDGE);
 
+	xt_compat_init_offsets(NFPROTO_BRIDGE, tmp.nentries);
 	ret = compat_copy_entries(entries_tmp, tmp.entries_size, &state);
 	if (ret < 0)
 		goto out_unlock;

net/netfilter/x_tables.c

@@ -455,6 +455,7 @@ void xt_compat_flush_offsets(u_int8_t af)
 		vfree(xt[af].compat_tab);
 		xt[af].compat_tab = NULL;
 		xt[af].number = 0;
+		xt[af].cur = 0;
 	}
 }
 EXPORT_SYMBOL_GPL(xt_compat_flush_offsets);
@@ -473,8 +474,7 @@ int xt_compat_calc_jump(u_int8_t af, unsigned int offset)
 		else
 			return mid ? tmp[mid - 1].delta : 0;
 	}
-	WARN_ON_ONCE(1);
-	return 0;
+	return left ? tmp[left - 1].delta : 0;
 }
 EXPORT_SYMBOL_GPL(xt_compat_calc_jump);