flush secondary addresses before primary ones

Unless promote_secondaries has been active deleting the primary address of
an interface will automatically delete all the secondary addresses.

In the case where ip flush requests the primary then secondary addresses to
be removed - which is the order the addresses are returned by the kernel -
this will cause an error as by the time the request to remove a secondary
address is made it will be missing as it will have been deleted in the
course of deleting the primary address.

This approach to solving this problem orders requests for the
deletion of secondary addresses before primary ones providing
rtnl_dump_filter_l(), a version of rtnl_dump_filter() that
iterates over a list of filters. And by providing two specialised
filters print_addrinfo_secondary() and print_addrinfo_primary().

rtnl_dump_filter_l() first iterates over all addresses using
print_addrinfo_secondary(), which appends secondary addresses to the
request buffer.  Then again using print_addrinfo_primary() which appends
primary addresses.

This approach should work regardless of it promote_secondaries is
active or not. And regardless of if any primary of secondary addresses
are present or not.
Signed-off-by: Simon Horman <horms@verge.net.au>

include/libnetlink.h

@@ -27,10 +27,22 @@ extern int rtnl_dump_request(struct rtnl_handle *rth, int type, void *req, int l
 
 typedef int (*rtnl_filter_t)(const struct sockaddr_nl *,
 			     struct nlmsghdr *n, void *);
+
+struct rtnl_dump_filter_arg
+{
+	rtnl_filter_t filter;
+	void *arg1;
+	rtnl_filter_t junk;
+	void *arg2;
+};
+
+extern int rtnl_dump_filter_l(struct rtnl_handle *rth,
+			      const struct rtnl_dump_filter_arg *arg);
 extern int rtnl_dump_filter(struct rtnl_handle *rth, rtnl_filter_t filter,
 			    void *arg1,
 			    rtnl_filter_t junk,
 			    void *arg2);
+
 extern int rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n, pid_t peer,
 		     unsigned groups, struct nlmsghdr *answer,
 		     rtnl_filter_t junk,

ip/ipaddress.c

@@ -539,6 +539,27 @@ int print_addrinfo(const struct sockaddr_nl *who, struct nlmsghdr *n,
 	return 0;
 }
 
+int print_addrinfo_primary(const struct sockaddr_nl *who, struct nlmsghdr *n,
+			   void *arg)
+{
+	struct ifaddrmsg *ifa = NLMSG_DATA(n);
+
+	if (!ifa->ifa_flags & IFA_F_SECONDARY)
+		return 0;
+
+	return print_addrinfo(who, n, arg);
+}
+
+int print_addrinfo_secondary(const struct sockaddr_nl *who, struct nlmsghdr *n,
+			     void *arg)
+{
+	struct ifaddrmsg *ifa = NLMSG_DATA(n);
+
+	if (ifa->ifa_flags & IFA_F_SECONDARY)
+		return 0;
+
+	return print_addrinfo(who, n, arg);
+}
 
 struct nlmsg_list
 {
@@ -700,12 +721,32 @@ static int ipaddr_list_or_flush(int argc, char **argv, int flush)
 		filter.flushe = sizeof(flushb);
 
 		while (round < MAX_ROUNDS) {
+			const struct rtnl_dump_filter_arg a[3] = {
+				{
+					.filter = print_addrinfo_secondary,
+					.arg1 = stdout,
+					.junk = NULL,
+					.arg2 = NULL
+				},
+				{
+					.filter = print_addrinfo_primary,
+					.arg1 = stdout,
+					.junk = NULL,
+					.arg2 = NULL
+				},
+				{
+					.filter = NULL,
+					.arg1 = NULL,
+					.junk = NULL,
+					.arg2 = NULL
+				},
+			};
 			if (rtnl_wilddump_request(&rth, filter.family, RTM_GETADDR) < 0) {
 				perror("Cannot send dump request");
 				exit(1);
 			}
 			filter.flushed = 0;
-			if (rtnl_dump_filter(&rth, print_addrinfo, stdout, NULL, NULL) < 0) {
+			if (rtnl_dump_filter_l(&rth, a) < 0) {
 				fprintf(stderr, "Flush terminated\n");
 				exit(1);
 			}

lib/libnetlink.c

@@ -172,11 +172,8 @@ int rtnl_dump_request(struct rtnl_handle *rth, int type, void *req, int len)
 	return sendmsg(rth->fd, &msg, 0);
 }
 
-int rtnl_dump_filter(struct rtnl_handle *rth,
-		     rtnl_filter_t filter,
-		     void *arg1,
-		     rtnl_filter_t junk,
-		     void *arg2)
+int rtnl_dump_filter_l(struct rtnl_handle *rth,
+		       const struct rtnl_dump_filter_arg *arg)
 {
 	struct sockaddr_nl nladdr;
 	struct iovec iov;
@@ -191,7 +188,7 @@ int rtnl_dump_filter(struct rtnl_handle *rth,
 	iov.iov_base = buf;
 	while (1) {
 		int status;
-		struct nlmsghdr *h;
+		const struct rtnl_dump_filter_arg *a;
 
 		iov.iov_len = sizeof(buf);
 		status = recvmsg(rth->fd, &msg, 0);
@@ -209,40 +206,45 @@ int rtnl_dump_filter(struct rtnl_handle *rth,
 			return -1;
 		}
 
-		h = (struct nlmsghdr*)buf;
-		while (NLMSG_OK(h, status)) {
-			int err;
+		for (a = arg; a->filter; a++) {
+			struct nlmsghdr *h = (struct nlmsghdr*)buf;
 
-			if (nladdr.nl_pid != 0 ||
-			    h->nlmsg_pid != rth->local.nl_pid ||
-			    h->nlmsg_seq != rth->dump) {
-				if (junk) {
-					err = junk(&nladdr, h, arg2);
-					if (err < 0)
-						return err;
+			while (NLMSG_OK(h, status)) {
+				int err;
+
+				if (nladdr.nl_pid != 0 ||
+				    h->nlmsg_pid != rth->local.nl_pid ||
+				    h->nlmsg_seq != rth->dump) {
+					if (a->junk) {
+						err = a->junk(&nladdr, h,
+							      a->arg2);
+						if (err < 0)
+							return err;
+					}
+					goto skip_it;
 				}
-				goto skip_it;
-			}
 
-			if (h->nlmsg_type == NLMSG_DONE)
-				return 0;
-			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;
-					perror("RTNETLINK answers");
+				if (h->nlmsg_type == NLMSG_DONE)
+					return 0;
+				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;
+						perror("RTNETLINK answers");
+					}
+					return -1;
 				}
-				return -1;
-			}
-			err = filter(&nladdr, h, arg1);
-			if (err < 0)
-				return err;
+				err = a->filter(&nladdr, h, a->arg1);
+				if (err < 0)
+					return err;
 
 skip_it:
-			h = NLMSG_NEXT(h, status);
-		}
+				h = NLMSG_NEXT(h, status);
+			}
+		} while (0);
 		if (msg.msg_flags & MSG_TRUNC) {
 			fprintf(stderr, "Message truncated\n");
 			continue;
@@ -254,6 +256,20 @@ skip_it:
 	}
 }
 
+int rtnl_dump_filter(struct rtnl_handle *rth,
+		     rtnl_filter_t filter,
+		     void *arg1,
+		     rtnl_filter_t junk,
+		     void *arg2)
+{
+	const struct rtnl_dump_filter_arg a[2] = {
+		{ .filter = filter, .arg1 = arg1, .junk = junk, .arg2 = arg2 },
+		{ .filter = NULL,   .arg1 = NULL, .junk = NULL, .arg2 = NULL }
+	};
+
+	return rtnl_dump_filter_l(rth, a);
+}
+
 int rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n, pid_t peer,
 	      unsigned groups, struct nlmsghdr *answer,
 	      rtnl_filter_t junk,