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>

networking/libiproute/ipaddress.c

@@ -23,6 +23,7 @@
 
 struct filter_t {
 	char *label;
+	/* Flush cmd buf. If !NULL, print_addrinfo() constructs flush commands in it */
 	char *flushb;
 	struct rtnl_handle *rth;
 	int scope, scopemask;
@@ -34,6 +35,8 @@ struct filter_t {
 	smallint showqueue;
 	smallint oneline;
 	smallint up;
+	/* Misnomer. Does not mean "flushed something" */
+	/* More like "flush commands were constructed by print_addrinfo()" */
 	smallint flushed;
 	inet_prefix pfx;
 } FIX_ALIASING;
@@ -201,7 +204,7 @@ static NOINLINE int print_linkinfo(const struct nlmsghdr *n)
 
 static int flush_update(void)
 {
-	if (rtnl_send(G_filter.rth, G_filter.flushb, G_filter.flushp) < 0) {
+	if (rtnl_send_check(G_filter.rth, G_filter.flushb, G_filter.flushp) < 0) {
 		bb_perror_msg("can't send flush request");
 		return -1;
 	}
@@ -510,7 +513,6 @@ int FAST_FUNC ipaddr_list_or_flush(char **argv, int flush)
 		xrtnl_dump_filter(&rth, store_nlmsg, &ainfo);
 	}
 
-
 	if (G_filter.family && G_filter.family != AF_PACKET) {
 		struct nlmsg_list **lp;
 		lp = &linfo;

networking/libiproute/ipneigh.c

@@ -32,7 +32,10 @@ struct filter_t {
 	int state;
 	int unused_only;
 	inet_prefix pfx;
+	/* Misnomer. Does not mean "flushed N something" */
+	/* More like "no_of_flush_commands_constructed_by_print_neigh()" */
 	int flushed;
+	/* Flush cmd buf. If !NULL, print_neigh() constructs flush commands in it */
 	char *flushb;
 	int flushp;
 	int flushe;
@@ -45,7 +48,7 @@ typedef struct filter_t filter_t;
 
 static int flush_update(void)
 {
-	if (rtnl_send(G_filter.rth, G_filter.flushb, G_filter.flushp) < 0) {
+	if (rtnl_send_check(G_filter.rth, G_filter.flushb, G_filter.flushp) < 0) {
 		bb_perror_msg("can't send flush request");
 		return -1;
 	}
@@ -299,9 +302,7 @@ static int FAST_FUNC ipneigh_list_or_flush(char **argv, int flush)
 		G_filter.rth = &rth;
 
 		while (round < MAX_ROUNDS) {
-			if (xrtnl_wilddump_request(&rth, G_filter.family, RTM_GETNEIGH) < 0) {
-				bb_perror_msg_and_die("can't send dump request");
-			}
+			xrtnl_wilddump_request(&rth, G_filter.family, RTM_GETNEIGH);
 			G_filter.flushed = 0;
 			if (xrtnl_dump_filter(&rth, print_neigh, NULL) < 0) {
 				bb_perror_msg_and_die("flush terminated");

networking/libiproute/iproute.c

@@ -26,7 +26,10 @@
 
 struct filter_t {
 	int tb;
+	/* Misnomer. Does not mean "flushed something" */
+	/* More like "flush commands were constructed by print_route()" */
 	smallint flushed;
+	/* Flush cmd buf. If !NULL, print_route() constructs flush commands in it */
 	char *flushb;
 	int flushp;
 	int flushe;
@@ -53,7 +56,7 @@ typedef struct filter_t filter_t;
 
 static int flush_update(void)
 {
-	if (rtnl_send(G_filter.rth, G_filter.flushb, G_filter.flushp) < 0) {
+	if (rtnl_send_check(G_filter.rth, G_filter.flushb, G_filter.flushp) < 0) {
 		bb_perror_msg("can't send flush request");
 		return -1;
 	}

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;
 
-	return xsendto(rth->fd, buf, len, (struct sockaddr*)&nladdr, sizeof(nladdr));
+	/* 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;
+	}
+
+	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)

networking/libiproute/libnetlink.h

@@ -20,7 +20,7 @@ struct rtnl_handle {
 
 extern void xrtnl_open(struct rtnl_handle *rth) FAST_FUNC;
 #define rtnl_close(rth) (close((rth)->fd))
-extern int xrtnl_wilddump_request(struct rtnl_handle *rth, int fam, int type) FAST_FUNC;
+extern void xrtnl_wilddump_request(struct rtnl_handle *rth, int fam, int type) FAST_FUNC;
 extern int rtnl_dump_request(struct rtnl_handle *rth, int type, void *req, int len) FAST_FUNC;
 extern int xrtnl_dump_filter(struct rtnl_handle *rth,
 		int (*filter)(const struct sockaddr_nl*, struct nlmsghdr *n, void*) FAST_FUNC,
@@ -34,8 +34,23 @@ extern int rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n, pid_t peer,
 		int (*junk)(struct sockaddr_nl *,struct nlmsghdr *n, void *),
 		void *jarg) FAST_FUNC;
 
-extern int rtnl_send(struct rtnl_handle *rth, char *buf, int) FAST_FUNC;
+int rtnl_send_check(struct rtnl_handle *rth, const void *buf, int len) FAST_FUNC;
+//TODO: pass rth->fd instead of full rth?
+static ALWAYS_INLINE void rtnl_send(struct rtnl_handle *rth, const void *buf, int len)
+{
+	// Used to be:
+	//struct sockaddr_nl nladdr;
+	//memset(&nladdr, 0, sizeof(nladdr));
+	//nladdr.nl_family = AF_NETLINK;
+	//return xsendto(rth->fd, buf, len, (struct sockaddr*)&nladdr, sizeof(nladdr));
 
+	// iproute2-4.2.0 simplified the above to:
+	//return send(rth->fd, buf, len, 0);
+
+	// We are using even shorter:
+	xwrite(rth->fd, buf, len);
+	// and convert to void, inline.
+}
 
 extern int addattr32(struct nlmsghdr *n, int maxlen, int type, uint32_t data) FAST_FUNC;
 extern int addattr_l(struct nlmsghdr *n, int maxlen, int type, void *data, int alen) FAST_FUNC;