net: introduce helper macro for_each_cmsghdr

Introduce helper macro for_each_cmsghdr as a wrapper of the enumerating
cmsghdr from msghdr, just cleanup.

Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/socket.h b/include/linux/socket.h
index 048d6d6eed6d..6e49a14365dc 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -103,6 +103,10 @@ struct cmsghdr {
                              (cmsg)->cmsg_len <= (unsigned long) \
                              ((mhdr)->msg_controllen - \
                               ((char *)(cmsg) - (char *)(mhdr)->msg_control)))
+#define for_each_cmsghdr(cmsg, msg) \
+        for (cmsg = CMSG_FIRSTHDR(msg); \
+             cmsg; \
+             cmsg = CMSG_NXTHDR(msg, cmsg))
 
 /*
  *      Get the next cmsg header