iface: handle EINTR case when creating the cache

If interface netlink dump is interrupted, then retry.

Before this patch, the netlink socket is reopened to drop stale dump
messages, instead empty the netlink queue and retry.

Reviewed-by: Eugene Crosser <crosser@average.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 38 insertions, 12 deletions

diff --git a/src/iface.c b/src/iface.c
index d0e1834c..c0642e0c 100644
--- a/src/iface.c
+++ b/src/iface.c
@@ -59,13 +59,13 @@ static int data_cb(const struct nlmsghdr *nlh, void *data)
 	return MNL_CB_OK;
 }
 
-void iface_cache_update(void)
+static int iface_mnl_talk(struct mnl_socket *nl, uint32_t portid)
 {
 	char buf[MNL_SOCKET_BUFFER_SIZE];
-	struct mnl_socket *nl;
 	struct nlmsghdr *nlh;
 	struct rtgenmsg *rt;
-	uint32_t seq, portid;
+	bool eintr = false;
+	uint32_t seq;
 	int ret;
 
 	nlh = mnl_nlmsg_put_header(buf);
@@ -75,6 +75,38 @@ void iface_cache_update(void)
 	rt = mnl_nlmsg_put_extra_header(nlh, sizeof(struct rtgenmsg));
 	rt->rtgen_family = AF_PACKET;
 
+	if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0)
+		return -1;
+
+	ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	while (ret > 0) {
+		ret = mnl_cb_run(buf, ret, seq, portid, data_cb, NULL);
+		if (ret == 0)
+			break;
+		if (ret < 0) {
+			if (errno != EINTR)
+				return ret;
+
+			/* process all pending messages before reporting EINTR */
+			eintr = true;
+		}
+		ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	}
+
+	if (eintr) {
+		ret = -1;
+		errno = EINTR;
+	}
+
+	return ret;
+}
+
+void iface_cache_update(void)
+{
+	struct mnl_socket *nl;
+	uint32_t portid;
+	int ret;
+
 	nl = mnl_socket_open(NETLINK_ROUTE);
 	if (nl == NULL)
 		netlink_init_error();
@@ -84,16 +116,10 @@ void iface_cache_update(void)
 
 	portid = mnl_socket_get_portid(nl);
 
-	if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0)
-		netlink_init_error();
+	do {
+		ret = iface_mnl_talk(nl, portid);
+	} while (ret < 0 && errno == EINTR);
 
-	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)
 		netlink_init_error();