[PATCH nft 2/2] Handle retriable errors from mnl functions

[Eugene Crosser <crosser@average.org>]

rc == -1 and errno == EINTR mean:

mnl_socket_recvfrom() - blindly rerun the function
mnl_cb_run()          - restart dump request from scratch

This commit introduces handling of both these conditions

Signed-off-by: Eugene Crosser <crosser@average.org>
---
 src/iface.c | 73 ++++++++++++++++++++++++++++++++---------------------
 1 file changed, 44 insertions(+), 29 deletions(-)

diff --git a/src/iface.c b/src/iface.c
index d0e1834c..029f6476 100644
--- a/src/iface.c
+++ b/src/iface.c
@@ -66,39 +66,54 @@ void iface_cache_update(void)
 	struct nlmsghdr *nlh;
 	struct rtgenmsg *rt;
 	uint32_t seq, portid;
+	bool need_restart;
+	int retry_count = 5;
 	int ret;
 
-	nlh = mnl_nlmsg_put_header(buf);
-	nlh->nlmsg_type	= RTM_GETLINK;
-	nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP;
-	nlh->nlmsg_seq = seq = time(NULL);
-	rt = mnl_nlmsg_put_extra_header(nlh, sizeof(struct rtgenmsg));
-	rt->rtgen_family = AF_PACKET;
-
-	nl = mnl_socket_open(NETLINK_ROUTE);
-	if (nl == NULL)
-		netlink_init_error();
-
-	if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0)
-		netlink_init_error();
-
-	portid = mnl_socket_get_portid(nl);
-
-	if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0)
-		netlink_init_error();
-
-	ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
-	while (ret > 0) {
-		ret = mnl_cb_run(buf, ret, seq, portid, data_cb, NULL);
-		if (ret <= MNL_CB_STOP)
-			break;
-		ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
-	}
-	if (ret == -1)
+	do {
+		nlh = mnl_nlmsg_put_header(buf);
+		nlh->nlmsg_type	= RTM_GETLINK;
+		nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP;
+		nlh->nlmsg_seq = seq = time(NULL);
+		rt = mnl_nlmsg_put_extra_header(nlh, sizeof(struct rtgenmsg));
+		rt->rtgen_family = AF_PACKET;
+
+		nl = mnl_socket_open(NETLINK_ROUTE);
+		if (nl == NULL)
+			netlink_init_error();
+
+		if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0)
+			netlink_init_error();
+
+		portid = mnl_socket_get_portid(nl);
+
+		if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0)
+			netlink_init_error();
+
+		need_restart = false;
+		while (true) {
+			ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+			if (ret == -1) {
+				if (errno == EINTR)
+					continue;
+				else
+					netlink_init_error();
+			}
+			ret = mnl_cb_run(buf, ret, seq, portid, data_cb, NULL);
+			if (ret == MNL_CB_STOP)
+				break;
+			if (ret == -1) {
+				if (errno == EINTR)
+					need_restart = true;
+				else
+					netlink_init_error();
+			}
+		}
+		mnl_socket_close(nl);
+	} while (need_restart && retry_count--);
+	if (need_restart)
 		netlink_init_error();
 
-	mnl_socket_close(nl);
-
 	iface_cache_init = true;
 }
 
-- 
2.32.0