[PATCH v4] netlink: Return prefix length for IPv6 addresses in nl_addr_get()

[Jon Maloy <jmaloy@redhat.com>]

nl_addr_get() was not setting the prefix_len output parameter for
IPv6 addresses, only for IPv4. This meant callers always got 0 for
IPv6, forcing them to use a hardcoded default (64).

Fix by assigning *prefix_len even in the IPv6 case.

Signed-off-by: Jon Maloy <jmaloy@redhat.com>

---
v2: - Simplified according to feedback from S. Brivio
    - Added test for AF_INET link local property
v3: - Corrected claim about convention for IPv4 link local address
      scope in commit log.
v4: - Reverted from the IPv4 link local exclusion change
---
 netlink.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/netlink.c b/netlink.c
index 82a2f0c..ee9a6b1 100644
--- a/netlink.c
+++ b/netlink.c
@@ -752,7 +752,7 @@ int nl_addr_set_ll_nodad(int s, unsigned int ifi)
  * @ifi:	Interface index in outer network namespace
  * @af:		Address family
  * @addr:	Global address to fill
- * @prefix_len:	Mask or prefix length, to fill (for IPv4)
+ * @prefix_len:	Mask or prefix length, to fill
  * @addr_l:	Link-scoped address to fill (for IPv6)
  *
  * Return: 0 on success, negative error code on failure
@@ -788,16 +788,11 @@ int nl_addr_get(int s, unsigned int ifi, sa_family_t af,
 			    (af == AF_INET6 && rta->rta_type != IFA_ADDRESS))
 				continue;
 
-			if (af == AF_INET && ifa->ifa_prefixlen > prefix_max) {
+			if (ifa->ifa_prefixlen > prefix_max &&
+			    (af == AF_INET || ifa->ifa_scope < RT_SCOPE_LINK)) {
 				memcpy(addr, RTA_DATA(rta), RTA_PAYLOAD(rta));
 
 				prefix_max = *prefix_len = ifa->ifa_prefixlen;
-			} else if (af == AF_INET6 && addr &&
-				   ifa->ifa_scope < RT_SCOPE_LINK &&
-				   ifa->ifa_prefixlen > prefix_max) {
-				memcpy(addr, RTA_DATA(rta), RTA_PAYLOAD(rta));
-
-				prefix_max = ifa->ifa_prefixlen;
 			}
 
 			if (addr_l &&
-- 
2.52.0