From 7a1a825c7b77785f256e05b1e3ac7676c7485a5c Mon Sep 17 00:00:00 2001
From: Karel Zak <kzak@redhat.com>
Date: Tue, 4 Jul 2017 12:50:39 +0200
Subject: [PATCH 135/135] login: use IPv4 on IPv4-mapping-to-IPv6

It seems that on some systems (e.g. RHEL7) the libc function
getaddrinfo() is not able to translate ::ffff: address to IPv4. The
result is 0.0.0.0 host address in the last(1) and utmpdump(1) output.

 /sbin/login -h "::ffff:192.168.1.7"

utmpdump:

  [7] [03926] [1   ] [user1   ] [pts/1       ] [::ffff:192.168.1.7  ] [0.0.0.0        ] [Thu May 12 17:49:50 2016    ]

Not sure if this is about order of the getaddrinfo() results, system
configuration or libc version. It's irrelevant for login(1). We have
to be robust enough to write usable address to log files everywhere.

The solution is to detect IPv4-mapping-to-IPv6 and use IPv4 for utmp.

Upstream: http://github.com/karelzak/util-linux/commit/1c8792f1ae7fa38cf1d4418ad99c207f65dfdb1a
Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1296233
Signed-off-by: Karel Zak <kzak@redhat.com>
---
 login-utils/login.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/login-utils/login.c b/login-utils/login.c
index e0e960f88..5c36953ef 100644
--- a/login-utils/login.c
+++ b/login-utils/login.c
@@ -1101,8 +1101,15 @@ static void init_remote_info(struct login_context *cxt, char *remotehost)
 		} else if (info->ai_family == AF_INET6) {
 			struct sockaddr_in6 *sa =
 				     (struct sockaddr_in6 *) info->ai_addr;
+#ifdef IN6_IS_ADDR_V4MAPPED
+			if (IN6_IS_ADDR_V4MAPPED(&sa->sin6_addr)) {
+				const uint8_t *bytes = sa->sin6_addr.s6_addr;
+				struct in_addr addr = { *(const in_addr_t *) (bytes + 12) };
 
-			memcpy(cxt->hostaddress, &(sa->sin6_addr), sizeof(sa->sin6_addr));
+				memcpy(cxt->hostaddress, &addr, sizeof(struct in_addr));
+			} else
+#endif
+				memcpy(cxt->hostaddress, &(sa->sin6_addr), sizeof(sa->sin6_addr));
 		}
 		freeaddrinfo(info);
 	}
-- 
2.13.6