udp_io, traceroute: Standardise IPv6 PKTINFO handling to be portable

The current standard (RFC 3542) is for IPV6_RECVPKTINFO to be given to
setsockopt, and IPV6_PKTINFO to be used as the packet type. Previously,
RFC 2292 required IPV6_PKTINFO to be used for both, but RFC 3542
re-purposed IPV6_PKTINFO when given to setsockopt. The special
Linux-specific IPV6_2292PKTINFO has the same semantics as IPV6_PKTINFO
in RFC 2292, but was introduced at the same time as IPV6_RECVPKTINFO.

Therefore, if we have IPV6_RECVPKTINFO available, we can use the RFC
3542 style, and if not, we assume that only the RFC 2292 API is
available, using IPV6_PKTINFO for both.

Signed-off-by: James Clarke <jrtc27@jrtc27.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 3 insertions, 5 deletions

diff --git a/networking/traceroute.c b/networking/traceroute.c
index df7122047..6dcbc2faa 100644
--- a/networking/traceroute.c
+++ b/networking/traceroute.c
@@ -311,6 +311,9 @@
 # ifndef SOL_IPV6
 #  define SOL_IPV6 IPPROTO_IPV6
 # endif
+# if defined(IPV6_PKTINFO) && !defined(IPV6_RECVPKTINFO)
+#  define IPV6_RECVPKTINFO IPV6_PKTINFO
+# endif
 #endif
 
 #include "libbb.h"
@@ -911,12 +914,7 @@ common_traceroute_main(int op, char **argv)
 #if ENABLE_TRACEROUTE6
         if (af == AF_INET6) {
                 xmove_fd(xsocket(AF_INET6, SOCK_RAW, IPPROTO_ICMPV6), rcvsock);
-# ifdef IPV6_RECVPKTINFO
                 setsockopt_1(rcvsock, SOL_IPV6, IPV6_RECVPKTINFO);
-                setsockopt_1(rcvsock, SOL_IPV6, IPV6_2292PKTINFO);
-# else
-                setsockopt_1(rcvsock, SOL_IPV6, IPV6_PKTINFO);
-# endif
         } else
 #endif
         {