2004-12-29 Greg Troxel <gdt@poblano.ir.bbn.com>
* sockopt.c (getsockopt_ipv4_ifindex): Document calling
convention. Beef up comments. Handle the case where the cmsghdr
has a zero controllen, or more specifically when the wanted option
is not present. This is needed for Solaris 8, and in general for
any platform for which configure finds a method and it can fail.
Mark some changes with XXX to be cleaned up post 0.98.
diff --git a/lib/sockopt.c b/lib/sockopt.c
index 8c518f8..f136615 100644
--- a/lib/sockopt.c
+++ b/lib/sockopt.c
@@ -280,63 +280,74 @@
return ret;
}
+/*
+ * Requires: msgh is not NULL and points to a valid struct msghdr, which
+ * may or may not have control data about the incoming interface.
+ *
+ * Returns the interface index (small integer >= 1) if it can be
+ * determined, or else 0.
+ */
static int
getsockopt_ipv4_ifindex (struct msghdr *msgh)
{
- /*
- * XXX: This routine's semantics are ill-defined, in particular how
- * the results "can't determine interface due to runtime behavior"
- * and "OS has no support for how to determine behavior" are
- * encoded. For now, return 0 for either case; caller must handle
- * as "don't know".
- */
+ /* XXX: initialize to zero? (Always overwritten, so just cosmetic.) */
int ifindex = -1;
- /*
- * If autoconf found a method to get ifindex, but it didn't work for
- * this packet, or on this OS, this routine can be entered with a
- * NULL cmsghdr pointer. Check msgh before using in each case
- * below, rather than here, to avoid having to ifdef twice, once for
- * declarations and once for code.
- */
-
#if defined(IP_PKTINFO)
/* Linux pktinfo based ifindex retrieval */
struct in_pktinfo *pktinfo;
- if (msgh == NULL)
- return 0;
-
pktinfo =
(struct in_pktinfo *)getsockopt_cmsg_data (msgh, IPPROTO_IP, IP_PKTINFO);
+ /* XXX Can pktinfo be NULL? Clean up post 0.98. */
ifindex = pktinfo->ipi_ifindex;
#elif defined(IP_RECVIF)
-/* BSD/other IP_RECVIF based ifindex retrieval */
+
+ /* retrieval based on IP_RECVIF */
+
#ifndef SUNOS_5
- /* RECVIF, but not SUNOS, so BSD */
+ /* BSD systems use a sockaddr_dl as the control message payload. */
struct sockaddr_dl *sdl;
+#else
+ /* SUNOS_5 uses an integer with the index. */
+ int *ifindex_p;
#endif /* SUNOS_5 */
- /* SUNOS_5 doesn't need a structure to extract ifindex */
-
- if (msgh == NULL)
- return 0;
#ifndef SUNOS_5
+ /* BSD */
sdl =
(struct sockaddr_dl *)getsockopt_cmsg_data (msgh, IPPROTO_IP, IP_RECVIF);
- ifindex = sdl->sdl_index;
-#else /* !SUNOS_5 */
- ifindex = *(uint_t *)getsockopt_cmsg_data (msgh, IPPROTO_IP, IP_RECVIF);
+ if (sdl != NULL)
+ ifindex = sdl->sdl_index;
+ else
+ ifindex = 0;
+#else
+ /*
+ * Solaris. On Solaris 8, IP_RECVIF is defined, but the call to
+ * enable it fails with errno=99, and the struct msghdr has
+ * controllen 0.
+ */
+ ifindex_p = (uint_t *)getsockopt_cmsg_data (msgh, IPPROTO_IP, IP_RECVIF);
+ if (ifindex_p != NULL)
+ ifindex = *ifindex_p;
+ else
+ ifindex = 0;
#endif /* SUNOS_5 */
-#else /* neither IP_PKTINFO nor IP_RECVIF, broken */
-
-#warning "getsockopt_ipv4_pktinfo_ifindex: dont have PKTINFO or RECVIF"
-#warning "things probably will be broken on this platform!"
- /* XXX why not -1 - this is a failure condition. */
+#else
+ /*
+ * Neither IP_PKTINFO nor IP_RECVIF defined - warn at compile time.
+ * XXX Decide if this is a core service, or if daemons have to cope.
+ * Since Solaris 8 and OpenBSD seem not to provide it, it seems that
+ * daemons have to cope.
+ */
+#warning "getsockopt_ipv4_ifindex: Neither IP_PKTINFO nor IP_RECVIF defined."
+#warning "Some daemons may fail to operate correctly!"
ifindex = 0;
+
#endif /* IP_PKTINFO */
+
return ifindex;
}