lib: fix comment for nl_recv() about return value for non-blocking read

Since commit 375a6294a41e003f873821a01d947f0ecfaf76d4, nl_recv()
would fail with -NLE_AGAIN if there is nothing to read. Fix the
documentation.

https://github.com/thom311/libnl/issues/129

1 files changed, 3 insertions, 1 deletions

diff --git a/lib/nl.c b/lib/nl.c
index f2c427b..1b4355b 100644
--- a/lib/nl.c
+++ b/lib/nl.c
@@ -621,7 +621,9 @@ errout:
  *
  * This function blocks until data is available to be read unless the socket
  * has been put into non-blocking mode using nl_socket_set_nonblocking() in
- * which case this function will return immediately with a return value of 0.
+ * which case this function will return immediately with a return value of
+ * -NLA_AGAIN (versions before 3.2.22 returned instead 0, in which case you
+ * should check first clear errno and then check for errno EAGAIN).
  *
  * The buffer size used when reading from the netlink socket and thus limiting
  * the maximum size of a netlink message that can be read defaults to the size