[Devel] [PATCH 5/5] netlink: avoid ENOBUF when a netlink queue is dumped

[Andrey Vagin]

From: Andrei Vagin <avagin at virtuozzo.com>

If a socket buffer is full and some messaged have been
dropped, the first recvmsg will return -ENOBUF.

We can avoid this if we set the NETLINK_NO_ENOBUFS opt for a socket.

Signed-off-by: Andrei Vagin <avagin at virtuozzo.com>
---
 criu/sk-netlink.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/criu/sk-netlink.c b/criu/sk-netlink.c
index 71bb77e..8ec4e90 100644
--- a/criu/sk-netlink.c
+++ b/criu/sk-netlink.c
@@ -151,6 +151,23 @@ static int dump_nl_opts(int sk, NlSkOptsEntry *e)
 	return ret;
 }
 
+static int dump_nl_queue(int sk, int id) {
+	int ret, old_val, on = 1;
+
+	if (dump_opt(sk, SOL_NETLINK, NETLINK_NO_ENOBUFS, &old_val))
+		return -1;
+
+	if (!old_val && restore_opt(sk, SOL_NETLINK, NETLINK_NO_ENOBUFS, &on))
+		return -1;
+
+	ret = dump_sk_queue(sk, id, SK_QUEUE_DUMP_ADDR);
+
+	if (!old_val && restore_opt(sk, SOL_NETLINK, NETLINK_NO_ENOBUFS, &old_val))
+		return -1;
+
+	return ret;
+}
+
 static int dump_one_netlink_fd(int lfd, u32 id, const struct fd_parms *p)
 {
 	struct netlink_sk_desc *sk;
@@ -217,7 +234,7 @@ static int dump_one_netlink_fd(int lfd, u32 id, const struct fd_parms *p)
 	if (dump_socket_opts(lfd, &skopts))
 		goto err;
 
-	if (kdat.has_nl_repair && dump_sk_queue(lfd, id, SK_QUEUE_DUMP_ADDR))
+	if (kdat.has_nl_repair && dump_nl_queue(lfd, id))
 		goto err;
 
 	if (pb_write_one(img_from_set(glob_imgset, CR_FD_NETLINK_SK), &ne, PB_NETLINK_SK))
-- 
1.8.3.1