>From 7da5a365c9908972726243b12b91666352c1ee31 Mon Sep 17 00:00:00 2001
From: Florian Weimer <fweimer@redhat.com>
Date: Wed, 27 Mar 2013 10:19:35 +0100
Subject: [PATCH 2/2] mnl_socket_peer_address: Add function to retrieve the
 sender address

This allows callers of mnl_socket_recvfrom to examine the address,
for instance, to give special treatment to messages sent by the kernel.

Signed-off-by: Florian Weimer <fweimer@redhat.com>
---
 include/libmnl/libmnl.h |  1 +
 src/libmnl.map          |  4 ++++
 src/socket.c            | 24 ++++++++++++++++++++----
 3 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/include/libmnl/libmnl.h b/include/libmnl/libmnl.h
index 5145ba5..74995fa 100644
--- a/include/libmnl/libmnl.h
+++ b/include/libmnl/libmnl.h
@@ -33,6 +33,7 @@ extern int mnl_socket_get_fd(struct mnl_socket *nl);
 extern unsigned int mnl_socket_get_portid(const struct mnl_socket *nl);
 extern ssize_t mnl_socket_sendto(struct mnl_socket *nl, const void *req, size_t siz);
 extern ssize_t mnl_socket_recvfrom(struct mnl_socket *nl, void *buf, size_t siz);
+extern struct sockaddr_nl *mnl_socket_peer_address(struct mnl_socket *nl);
 extern int mnl_socket_setsockopt(struct mnl_socket *nl, int type, void *buf, socklen_t len);
 extern int mnl_socket_getsockopt(const struct mnl_socket *nl, int type, void *buf, socklen_t *len);
 
diff --git a/src/libmnl.map b/src/libmnl.map
index dbc332e..626ea87 100644
--- a/src/libmnl.map
+++ b/src/libmnl.map
@@ -69,6 +69,10 @@ global:
 local: *;
 };
 
+LIBMNL_1.0.3 {
+  mnl_socket_peer_address;
+};
+
 LIBMNL_1.1 {
   mnl_attr_parse_payload;
 } LIBMNL_1.0;
diff --git a/src/socket.c b/src/socket.c
index c77af91..1d956a0 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -8,6 +8,7 @@
  */
 
 #include <libmnl/libmnl.h>
+#include <string.h>
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <stdlib.h>
@@ -69,6 +70,7 @@
 struct mnl_socket {
 	int 			fd;
 	struct sockaddr_nl	addr;
+	struct sockaddr_nl	peer;
 };
 
 /**
@@ -206,14 +208,13 @@ ssize_t
 mnl_socket_recvfrom(struct mnl_socket *nl, void *buf, size_t bufsiz)
 {
 	ssize_t ret;
-	struct sockaddr_nl addr;
 	struct iovec iov = {
 		.iov_base	= buf,
 		.iov_len	= bufsiz,
 	};
 	struct msghdr msg = {
-		.msg_name	= &addr,
-		.msg_namelen	= sizeof(struct sockaddr_nl),
+		.msg_name	= &nl->peer,
+		.msg_namelen	= sizeof(nl->peer),
 		.msg_iov	= &iov,
 		.msg_iovlen	= 1,
 		.msg_control	= NULL,
@@ -221,8 +222,10 @@ mnl_socket_recvfrom(struct mnl_socket *nl, void *buf, size_t bufsiz)
 		.msg_flags	= 0,
 	};
 	ret = recvmsg(nl->fd, &msg, 0);
-	if (ret == -1)
+	if (ret == -1) {
+		memset(&nl->peer, 0, sizeof(nl->peer));
 		return ret;
+	}
 
 	if (msg.msg_flags & MSG_TRUNC) {
 		errno = ENOSPC;
@@ -237,6 +240,19 @@ mnl_socket_recvfrom(struct mnl_socket *nl, void *buf, size_t bufsiz)
 EXPORT_SYMBOL(mnl_socket_recvfrom);
 
 /**
+ * mnl_socket_peer_address - return the sender of the last message
+ *
+ * The address is only valid after a successful call to
+ * mnl_socket_recvfrom().  The returned pointer is valid until
+ * mnl_socket_close() is called; it must not be freed by the caller.
+ */
+struct sockaddr_nl *
+mnl_socket_peer_address(struct mnl_socket *nl)
+{
+	return &nl->peer;
+}
+
+/**
  * mnl_socket_close - close a given netlink socket
  * \param nl netlink socket obtained via mnl_socket_open()
  *
-- 
1.8.1.4