cfg: Request and check return valuev0.2

Request the return value of the operation from the kernel and check if
it's an error, to inform the user about e.g. not having sufficient
permission.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

1 files changed, 15 insertions, 1 deletions

diff --git a/src/cfg.c b/src/cfg.c
index 79dec37..dc6082b 100644
--- a/src/cfg.c
+++ b/src/cfg.c
@@ -1,4 +1,5 @@
 #include <err.h>
+#include <errno.h>
 #include <limits.h>
 #include <linux/netlink.h>
 #include <linux/rtnetlink.h>
@@ -25,6 +26,10 @@ int main(int argc, char **argv)
 		struct ifaddrmsg ifa;
 		char attrbuf[32];
 	} req;
+	struct {
+		struct nlmsghdr nh;
+		struct nlmsgerr err;
+	} resp;
 	struct rtattr *rta;
 	unsigned long addrul;
 	uint32_t addr;
@@ -46,7 +51,7 @@ int main(int argc, char **argv)
 
 	memset(&req, 0, sizeof(req));
 	req.nh.nlmsg_len = NLMSG_SPACE(sizeof(struct ifaddrmsg));
-	req.nh.nlmsg_flags = NLM_F_REQUEST;
+	req.nh.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
 	req.nh.nlmsg_type = RTM_NEWADDR;
 	req.ifa.ifa_family = AF_QIPCRTR;
 
@@ -61,5 +66,14 @@ int main(int argc, char **argv)
 	if (ret < 0)
 		err(1, "failed to send netlink request");
 
+	ret = recv(sock, &resp, sizeof(resp), 0);
+	if (ret < 0)
+		err(1, "failed to receive netlink response");
+
+	if (resp.nh.nlmsg_type == NLMSG_ERROR && resp.err.error != 0) {
+		errno = -resp.err.error;
+		err(1, "failed to configure node id");
+	}
+
 	return 0;
 }