ip: use rtnl_send_check() on flush commands, closes 6962

function                                             old     new   delta
rtnl_send_check                                        -     160    +160
xrtnl_wilddump_request                                64      66      +2
ipneigh_list_or_flush                                714     706      -8
rtnl_send                                             69       -     -69
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 1/1 up/down: 162/-77)            Total: 85 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 35 insertions, 8 deletions

diff --git a/networking/libiproute/libnetlink.c b/networking/libiproute/libnetlink.c
index 40955fcae..b0d4166ac 100644
--- a/networking/libiproute/libnetlink.c
+++ b/networking/libiproute/libnetlink.c
@@ -34,7 +34,7 @@ void FAST_FUNC xrtnl_open(struct rtnl_handle *rth/*, unsigned subscriptions*/)
 	rth->seq = time(NULL);
 }
 
-int FAST_FUNC xrtnl_wilddump_request(struct rtnl_handle *rth, int family, int type)
+void FAST_FUNC xrtnl_wilddump_request(struct rtnl_handle *rth, int family, int type)
 {
 	struct {
 		struct nlmsghdr nlh;
@@ -48,18 +48,45 @@ int FAST_FUNC xrtnl_wilddump_request(struct rtnl_handle *rth, int family, int ty
 	req.nlh.nlmsg_seq = rth->dump = ++rth->seq;
 	req.g.rtgen_family = family;
 
-	return rtnl_send(rth, (void*)&req, sizeof(req));
+	rtnl_send(rth, (void*)&req, sizeof(req));
 }
 
-//TODO: pass rth->fd instead of full rth?
-int FAST_FUNC rtnl_send(struct rtnl_handle *rth, char *buf, int len)
+/* A version which checks for e.g. EPERM errors.
+ * Try: setuidgid 1:1 ip addr flush dev eth0
+ */
+int FAST_FUNC rtnl_send_check(struct rtnl_handle *rth, const void *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;
+	status = write(rth->fd, buf, len);
+	if (status < 0)
+		return status;
+
+	/* Check for immediate errors */
+	status = recv(rth->fd, resp, sizeof(resp), MSG_DONTWAIT|MSG_PEEK);
+	if (status < 0) {
+		if (errno == EAGAIN) /* if no error, this happens */
+			return 0;
+		return -1;
+	}
 
-	return xsendto(rth->fd, buf, len, (struct sockaddr*)&nladdr, sizeof(nladdr));
+	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)))
+				bb_error_msg("ERROR truncated");
+			else
+				errno = -err->error;
+			return -1;
+		}
+	}
+
+	return 0;
 }
 
 int FAST_FUNC rtnl_dump_request(struct rtnl_handle *rth, int type, void *req, int len)