From be0c22a46cfb79ab2342bb28fde99afa94ef868e Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Wed, 18 Feb 2009 01:40:43 +0000 Subject: netlink: add NETLINK_BROADCAST_ERROR socket option This patch adds NETLINK_BROADCAST_ERROR which is a netlink socket option that the listener can set to make netlink_broadcast() return errors in the delivery to the caller. This option is useful if the caller of netlink_broadcast() do something with the result of the message delivery, like in ctnetlink where it drops a network packet if the event delivery failed, this is used to enable reliable logging and state-synchronization. If this socket option is not set, netlink_broadcast() only reports ESRCH errors and silently ignore ENOBUFS errors, which is what most netlink_broadcast() callers should do. This socket option is based on a suggestion from Patrick McHardy. Patrick McHardy can exchange this patch for a beer from me ;). Signed-off-by: Pablo Neira Ayuso Acked-by: Patrick McHardy Signed-off-by: David S. Miller --- include/linux/netlink.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/netlink.h') diff --git a/include/linux/netlink.h b/include/linux/netlink.h index 51b09a1f46c..1e6bf995435 100644 --- a/include/linux/netlink.h +++ b/include/linux/netlink.h @@ -103,6 +103,7 @@ struct nlmsgerr #define NETLINK_ADD_MEMBERSHIP 1 #define NETLINK_DROP_MEMBERSHIP 2 #define NETLINK_PKTINFO 3 +#define NETLINK_BROADCAST_ERROR 4 struct nl_pktinfo { -- cgit v1.2.3 From 38938bfe3489394e2eed5e40c9bb8f66a2ce1405 Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Tue, 24 Mar 2009 16:37:55 -0700 Subject: netlink: add NETLINK_NO_ENOBUFS socket flag This patch adds the NETLINK_NO_ENOBUFS socket flag. This flag can be used by unicast and broadcast listeners to avoid receiving ENOBUFS errors. Generally speaking, ENOBUFS errors are useful to notify two things to the listener: a) You may increase the receiver buffer size via setsockopt(). b) You have lost messages, you may be out of sync. In some cases, ignoring ENOBUFS errors can be useful. For example: a) nfnetlink_queue: this subsystem does not have any sort of resync method and you can decide to ignore ENOBUFS once you have set a given buffer size. b) ctnetlink: you can use this together with the socket flag NETLINK_BROADCAST_SEND_ERROR to stop getting ENOBUFS errors as you do not need to resync (packets whose event are not delivered are drop to provide reliable logging and state-synchronization). Moreover, the use of NETLINK_NO_ENOBUFS also reduces a "go up, go down" effect in terms of performance which is due to the netlink congestion control when the listener cannot back off. The effect is the following: 1) throughput rate goes up and netlink messages are inserted in the receiver buffer. 2) Then, netlink buffer fills and overruns (set on nlk->state bit 0). 3) While the listener empties the receiver buffer, netlink keeps dropping messages. Thus, throughput goes dramatically down. 4) Then, once the listener has emptied the buffer (nlk->state bit 0 is set off), goto step 1. This effect is easy to trigger with netlink broadcast under heavy load, and it is more noticeable when using a big receiver buffer. You can find some results in [1] that show this problem. [1] http://1984.lsi.us.es/linux/netlink/ This patch also includes the use of sk_drop to account the number of netlink messages drop due to overrun. This value is shown in /proc/net/netlink. Signed-off-by: Pablo Neira Ayuso Signed-off-by: David S. Miller --- include/linux/netlink.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/netlink.h') diff --git a/include/linux/netlink.h b/include/linux/netlink.h index 1e6bf995435..5ba398e9030 100644 --- a/include/linux/netlink.h +++ b/include/linux/netlink.h @@ -104,6 +104,7 @@ struct nlmsgerr #define NETLINK_DROP_MEMBERSHIP 2 #define NETLINK_PKTINFO 3 #define NETLINK_BROADCAST_ERROR 4 +#define NETLINK_NO_ENOBUFS 5 struct nl_pktinfo { -- cgit v1.2.3