Add a queue to hold packets while we await an ARP reply.

When a fast machine first brings up some non TCP networking program
it is quite possible that we will drop packets due to the fact that
only one packet can be held per ARP entry.  This leads to packets
being missed when a program starts or restarts if the ARP data is
not currently in the ARP cache.

This code adds a new sysctl, net.link.ether.inet.maxhold, which defines
a system wide maximum number of packets to be held in each ARP entry.
Up to maxhold packets are queued until an ARP reply is received or
the ARP times out.  The default setting is the old value of 1
which has been part of the BSD networking code since time
immemorial.

Expose the time we hold an incomplete ARP entry by adding
the sysctl net.link.ether.inet.wait, which defaults to 20
seconds, the value used when the new ARP code was added..

Reviewed by:	bz, rpaulo
MFC after: 3 weeks

1 files changed, 2 insertions, 1 deletions

diff --git a/sys/net/if_llatbl.h b/sys/net/if_llatbl.h
index a4d02ab..6c5ad18 100644
--- a/sys/net/if_llatbl.h
+++ b/sys/net/if_llatbl.h
@@ -58,6 +58,7 @@ struct llentry {
 	struct lltable		 *lle_tbl;
 	struct llentries	 *lle_head;
 	struct mbuf		 *la_hold;
+	int     		 la_numheld;  /* # of packets currently held */
 	time_t			 la_expire;
 	uint16_t		 la_flags;    
 	uint16_t		 la_asked;
@@ -191,7 +192,7 @@ void		lltable_drain(int);
 #endif
 int		lltable_sysctl_dumparp(int, struct sysctl_req *);
 
-void		llentry_free(struct llentry *);
+size_t		llentry_free(struct llentry *);
 int		llentry_update(struct llentry **, struct lltable *,
                        struct sockaddr_storage *, struct ifnet *);