From: Alexander Aring <alex.aring@gmail.com>
Date: Fri, 27 Mar 2020 18:00:19 -0400
Subject: addrconf: add functionality to check on rpl requirements
Patch-mainline: v5.7-rc1
Git-commit: f37c6059363403d528acf8d530bb6e8a5666a875
References: bsc#1176447

This patch adds a functionality to addrconf to check on a specific RPL
address configuration. According to RFC 6554:

To detect loops in the SRH, a router MUST determine if the SRH
includes multiple addresses assigned to any interface on that
router. If such addresses appear more than once and are separated by
at least one address not assigned to that router.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 include/net/addrconf.h |    3 ++
 net/ipv6/addrconf.c    |   53 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+)

--- a/include/net/addrconf.h
+++ b/include/net/addrconf.h
@@ -90,6 +90,9 @@ int ipv6_chk_addr_and_flags(struct net *
 int ipv6_chk_home_addr(struct net *net, const struct in6_addr *addr);
 #endif
 
+int ipv6_chk_rpl_srh_loop(struct net *net, const struct in6_addr *segs,
+			  unsigned char nsegs);
+
 bool ipv6_chk_custom_prefix(const struct in6_addr *addr,
 				   const unsigned int prefix_len,
 				   struct net_device *dev);
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4400,6 +4400,59 @@ int ipv6_chk_home_addr(struct net *net,
 }
 #endif
 
+/* RFC6554 has some algorithm to avoid loops in segment routing by
+ * checking if the segments contains any of a local interface address.
+ *
+ * Quote:
+ *
+ * To detect loops in the SRH, a router MUST determine if the SRH
+ * includes multiple addresses assigned to any interface on that router.
+ * If such addresses appear more than once and are separated by at least
+ * one address not assigned to that router.
+ */
+int ipv6_chk_rpl_srh_loop(struct net *net, const struct in6_addr *segs,
+			  unsigned char nsegs)
+{
+	const struct in6_addr *addr;
+	int i, ret = 0, found = 0;
+	struct inet6_ifaddr *ifp;
+	bool separated = false;
+	unsigned int hash;
+	bool hash_found;
+
+	rcu_read_lock();
+	for (i = 0; i < nsegs; i++) {
+		addr = &segs[i];
+		hash = inet6_addr_hash(net, addr);
+
+		hash_found = false;
+		hlist_for_each_entry_rcu(ifp, &inet6_addr_lst[hash], addr_lst) {
+			if (!net_eq(dev_net(ifp->idev->dev), net))
+				continue;
+
+			if (ipv6_addr_equal(&ifp->addr, addr)) {
+				hash_found = true;
+				break;
+			}
+		}
+
+		if (hash_found) {
+			if (found > 1 && separated) {
+				ret = 1;
+				break;
+			}
+
+			separated = false;
+			found++;
+		} else {
+			separated = true;
+		}
+	}
+	rcu_read_unlock();
+
+	return ret;
+}
+
 /*
  *	Periodic address status verification
  */