[IPV6]: Use bitfields for hop_limit and mcast_hops.

Save some bits for future extensions.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>

1 files changed, 24 insertions, 4 deletions

diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 9b59e37afad9..87ae4e389ce1 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -274,8 +274,29 @@ struct ipv6_pinfo {
 
         __be32                  flow_label;
         __u32                   frag_size;
-        __s16                   hop_limit;
-        __s16                   mcast_hops;
+
+        /*
+         * Packed in 16bits.
+         * Omit one shift by by putting the signed field at MSB.
+         */
+#if defined(__BIG_ENDIAN_BITFIELD)
+        __s16                   hop_limit:9;
+        __u16                   __unused_1:7;
+#else
+        __u16                   __unused_1:7;
+        __s16                   hop_limit:9;
+#endif
+
+#if defined(__BIG_ENDIAN_BITFIELD)
+        /* Packed in 16bits. */
+        __s16                   mcast_hops:9;
+        __u16                   __unused_2:6,
+                                mc_loop:1;
+#else
+        __u16                   mc_loop:1,
+                                __unused_2:6;
+        __s16                   mcast_hops:9;
+#endif
         int                     mcast_oif;
 
         /* pktoption flags */
@@ -298,8 +319,7 @@ struct ipv6_pinfo {
         } rxopt;
 
         /* sockopt flags */
-        __u8                    mc_loop:1,
-                                recverr:1,
+        __u8                    recverr:1,
                                 sndflow:1,
                                 pmtudisc:2,
                                 ipv6only:1;