From: Stephen Hemminger <stephen.hemminger@vyatta.com>
Date: Sat, 26 Jan 2008 19:09:42 +0000 (-0800)
Subject: poll for errors after rtnl_send
X-Git-Tag: v2.6.25~43
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=54bb35c69cec6c730a4ac95530a1d2ca6670f73b;p=thirdparty%2Fiproute2.git

poll for errors after rtnl_send

This fixes the problem where a bulk operation (like ip flush)
is performed as non-root user.  The kernel will only send a response
if there is an error, so check for it.
---

diff --git a/lib/libnetlink.c b/lib/libnetlink.c
index 7876c190b..a4e91cf7c 100644
--- a/lib/libnetlink.c
+++ b/lib/libnetlink.c
@@ -114,11 +114,39 @@ int rtnl_wilddump_request(struct rtnl_handle *rth, int family, int type)
 int rtnl_send(struct rtnl_handle *rth, const char *buf, int len)
 {
 	struct sockaddr_nl nladdr;
+	struct nlmsghdr *h;
+	int status;
+	char resp[1024];
 
 	memset(&nladdr, 0, sizeof(nladdr));
 	nladdr.nl_family = AF_NETLINK;
 
-	return sendto(rth->fd, buf, len, 0, (struct sockaddr*)&nladdr, sizeof(nladdr));
+	status = sendto(rth->fd, buf, len, 0, 
+		     (struct sockaddr*)&nladdr, sizeof(nladdr));
+	if (status < 0)
+		return status;
+
+	/* Check for errors */
+	status = recv(rth->fd, resp, sizeof(resp), MSG_DONTWAIT);
+	if (status < 0) {
+		if (errno == EAGAIN)
+			return 0;
+		return -1;
+	}
+
+	for (h = (struct nlmsghdr *)resp; NLMSG_OK(h, status);
+	     h = NLMSG_NEXT(h, status)) {
+		if (h->nlmsg_type == NLMSG_ERROR) {
+			struct nlmsgerr *err = (struct nlmsgerr*)NLMSG_DATA(h);
+			if (h->nlmsg_len < NLMSG_LENGTH(sizeof(struct nlmsgerr)))
+				fprintf(stderr, "ERROR truncated\n");
+			else 
+				errno = -err->error;
+		}
+		return -1;
+	}
+
+	return 0;
 }
 
 int rtnl_dump_request(struct rtnl_handle *rth, int type, void *req, int len)