[libvirt] [PATCH v4] libvirtd: Increase NL buffer size for lots of interface

[Leno Hou]

1. When switching CPUs to offline/online in a system more than 128 cpus
2. When using virsh to destroy domain in a system with more interface
All of above happens nl_recv returned with error: No buffer space available.

This patch sets the socket buffer size to 128K and turns on message peeking
on new function virNetlinkAlloc,as this would solve this problem totally
and permanetly.

Signed-off-by: Leno Hou <houqy at linux.vnet.ibm.com>
Cc: Wenyi Gao <wenyi at linux.vnet.ibm.com>
CC: Laine Stump <laine at laine.org>
CC: Michal Privoznik <mprivozn at redhat.com>
---
 src/util/virnetlink.c | 42 ++++++++++++++++++++++++++++++++++++++----
 src/util/virnetlink.h |  7 +++++++
 2 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/src/util/virnetlink.c b/src/util/virnetlink.c
index 679b48e..02f5215 100644
--- a/src/util/virnetlink.c
+++ b/src/util/virnetlink.c
@@ -64,13 +64,11 @@ struct virNetlinkEventHandle {
 };
 
 # ifdef HAVE_LIBNL1
-#  define virNetlinkAlloc nl_handle_alloc
+#  define virSocketSetBufferSize nl_set_buffer_size
 #  define virNetlinkFree nl_handle_destroy
-typedef struct nl_handle virNetlinkHandle;
 # else
-#  define virNetlinkAlloc nl_socket_alloc
+#  define virSocketSetBufferSize nl_socket_set_buffer_size
 #  define virNetlinkFree nl_socket_free
-typedef struct nl_sock virNetlinkHandle;
 # endif
 
 typedef struct _virNetlinkEventSrvPrivate virNetlinkEventSrvPrivate;
@@ -108,6 +106,42 @@ static virNetlinkHandle *placeholder_nlhandle;
 /* Function definitions */
 
 /**
+ * virNetlinkAlloc
+ *
+ * Perform netlink allocation which was defined differently for libnl3
+ * vs libnl-1, and did all of three in one function
+ *  1) create socket
+ *  2) set larger buffer size
+ *  3) turn on message peeking
+ *
+ *  see the following email message:
+ *  https://www.redhat.com/archives/libvir-list/2016-January/msg00536.html
+ *
+ *  Returns virNetlinkHandle
+ */
+virNetlinkHandle *virNetlinkAlloc(void)
+{
+    virNetlinkHandle *netlinknh;
+    #ifdef HAVE_LIBNL1
+    netlinknh = nl_handle_alloc();
+    #else
+    netlinknh = nl_socket_alloc();
+    #endif
+
+    if (virSocketSetBufferSize(netlinknh,131702,0) >= 0) {
+        nl_socket_enable_msg_peek(netlinknh);
+        return netlinknh;
+    }
+
+    virReportSystemError(errno,
+            "%s",_("can not set socket buffer size to 128k"));
+
+    virNetlinkFree(netlinknh);
+
+    return NULL;
+}
+
+/**
  * virNetlinkStartup:
  *
  * Perform any initialization that needs to take place before the
diff --git a/src/util/virnetlink.h b/src/util/virnetlink.h
index 0664a7a..b4a2010 100644
--- a/src/util/virnetlink.h
+++ b/src/util/virnetlink.h
@@ -44,6 +44,13 @@ struct nlmsghdr;
 
 # endif /* __linux__ */
 
+# ifdef HAVE_LIBNL1
+typedef struct nl_handle virNetlinkHandle;
+# else
+typedef struct nl_sock virNetlinkHandle;
+# endif
+virNetlinkHandle *virNetlinkAlloc(void);
+
 int virNetlinkStartup(void);
 void virNetlinkShutdown(void);
 
-- 
1.9.1