getifaddrs: Don't return ifa entries with NULL names [BZ #21812]

A lookup operation in map_newlink could turn 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.

diff --git a/ChangeLog b/ChangeLog
index 1f35f29d775decdc9c650f527d36ee32fcf52b33..d09fb5ece4578438507c5bad35aaacbdc8fed49b 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2018-06-29  Daniel Alvarez  <dalvarez@redhat.com>
+           Jakub Sitnicki  <jkbs@redhat.com>
+
+       [BZ #21812]
+       * sysdeps/unix/sysv/linux/ifaddrs.c (getifaddrs_internal): Retry
+       on NLM_F_DUMP_INTR.
+
 2018-06-28  Szabolcs Nagy  <szabolcs.nagy@arm.com>
 
        * manual/llio.texi: Remove spurious space.

diff --git a/sysdeps/unix/sysv/linux/ifaddrs.c b/sysdeps/unix/sysv/linux/ifaddrs.c
index 32381f54e4e0e10c42c47aed0ebeb1df03bf19af..ac0e1e5738f3a24fd576306a58c0c65e2e018d9b 100644 (file)
--- 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 rely 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 */