[PATCH] [BZ #21812] getifaddrs() Don't return ifa entries with NULL names

[Daniel Alvarez <dalvarez@redhat.com>]

Due to bug 21812, a lookup operation in map_newlink() turns out
into an insert because of holes in the interface part of the map.
This leads to incorrectly set the name of the interface to NULL when
the interface is not present for the address being processed (most
likely because the interface was added between the RTM_GETLINK and
RTM_GETADDR calls to the kernel). When such changes are detected
by the kernel, it'll mark the dump as "inconsistent" by setting
NLM_F_DUMP_INTR flag on the next netlink message.

This patch checks this condition and retries the whole operation.
Hopes are that next time the interface corresponding to the address
entry is present in the list and correct name is returned.

Signed-off-by: Daniel Alvarez <dalvarez@redhat.com>
Signed-off-by: Jakub Sitnicki <jkbs@redhat.com>
---
 sysdeps/unix/sysv/linux/ifaddrs.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/sysdeps/unix/sysv/linux/ifaddrs.c b/sysdeps/unix/sysv/linux/ifaddrs.c
index 32381f54e4..5659c9605b 100644
--- a/sysdeps/unix/sysv/linux/ifaddrs.c
+++ b/sysdeps/unix/sysv/linux/ifaddrs.c
@@ -370,6 +370,14 @@ getifaddrs_internal (struct ifaddrs **ifap)
 	  if ((pid_t) nlh->nlmsg_pid != nh.pid || nlh->nlmsg_seq != nlp->seq)
 	    continue;
 
+      /* If the dump got interrupted, we can't relay on the results so
+         try again. */
+      if (nlh->nlmsg_flags & NLM_F_DUMP_INTR)
+        {
+          result = -EAGAIN;
+          goto exit_free;
+        }
+
 	  if (nlh->nlmsg_type == NLMSG_DONE)
 	    break;		/* ok */
 
-- 
2.15.1 (Apple Git-101)