From 4e5507512067ff31d4f2118a4202dec750bff383 Mon Sep 17 00:00:00 2001
From: bluhm <bluhm@openbsd.org>
Date: Mon, 26 Apr 2021 07:55:16 +0000
Subject: [PATCH] Convert the ARP packet hold queue from mbuf list to mbuf
 queue which contins a mutex.  Update la_hold_total with atomic operations. OK
 sashan@

---
 sys/netinet/if_ether.c | 48 ++++++++++++++++++------------------------
 1 file changed, 20 insertions(+), 28 deletions(-)

diff --git a/sys/netinet/if_ether.c b/sys/netinet/if_ether.c
index 79ea9e139df..bdc5d5fd360 100644
--- a/sys/netinet/if_ether.c
+++ b/sys/netinet/if_ether.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if_ether.c,v 1.245 2021/04/23 21:55:36 bluhm Exp $	*/
+/*	$OpenBSD: if_ether.c,v 1.246 2021/04/26 07:55:16 bluhm Exp $	*/
 /*	$NetBSD: if_ether.c,v 1.31 1996/05/11 12:59:58 mycroft Exp $	*/
 
 /*
@@ -68,7 +68,7 @@
 struct llinfo_arp {
 	LIST_ENTRY(llinfo_arp)	 la_list;
 	struct rtentry		*la_rt;		/* backpointer to rtentry */
-	struct mbuf_list	 la_ml;		/* packet hold queue */
+	struct mbuf_queue	 la_mq;		/* packet hold queue */
 	time_t			 la_refreshed;	/* when was refresh sent */
 	int			 la_asked;	/* number of queries sent */
 };
@@ -189,7 +189,7 @@ arp_rtrequest(struct ifnet *ifp, int req, struct rtentry *rt)
 			break;
 		}
 
-		ml_init(&la->la_ml);
+		mq_init(&la->la_mq, LA_HOLD_QUEUE, IPL_SOFTNET);
 		la->la_rt = rt;
 		rt->rt_flags |= RTF_LLINFO;
 		if ((rt->rt_flags & RTF_LOCAL) == 0)
@@ -203,7 +203,7 @@ arp_rtrequest(struct ifnet *ifp, int req, struct rtentry *rt)
 		LIST_REMOVE(la, la_list);
 		rt->rt_llinfo = NULL;
 		rt->rt_flags &= ~RTF_LLINFO;
-		la_hold_total -= ml_purge(&la->la_ml);
+		atomic_sub_int(&la_hold_total, mq_purge(&la->la_mq));
 		pool_put(&arp_pool, la);
 		break;
 
@@ -374,18 +374,11 @@ arpresolve(struct ifnet *ifp, struct rtentry *rt0, struct mbuf *m,
 	 * response yet. Insert mbuf in hold queue if below limit
 	 * if above the limit free the queue without queuing the new packet.
 	 */
-	if (la_hold_total < LA_HOLD_TOTAL) {
-		struct mbuf *mh;
-
-		if (ml_len(&la->la_ml) >= LA_HOLD_QUEUE) {
-			mh = ml_dequeue(&la->la_ml);
-			la_hold_total--;
-			m_freem(mh);
-		}
-		ml_enqueue(&la->la_ml, m);
-		la_hold_total++;
+	if (atomic_inc_int_nv(&la_hold_total) <= LA_HOLD_TOTAL) {
+		if (mq_push(&la->la_mq, m) != 0)
+			atomic_dec_int(&la_hold_total);
 	} else {
-		la_hold_total -= ml_purge(&la->la_ml);
+		atomic_sub_int(&la_hold_total, mq_purge(&la->la_mq) + 1);
 		m_freem(m);
 	}
 
@@ -414,7 +407,8 @@ arpresolve(struct ifnet *ifp, struct rtentry *rt0, struct mbuf *m,
 				rt->rt_expire += arpt_down;
 				la->la_asked = 0;
 				la->la_refreshed = 0;
-				la_hold_total -= ml_purge(&la->la_ml);
+				atomic_sub_int(&la_hold_total,
+				    mq_purge(&la->la_mq));
 			}
 		}
 	}
@@ -600,7 +594,7 @@ arpcache(struct ifnet *ifp, struct ether_arp *ea, struct rtentry *rt)
 	struct in_addr *spa = (struct in_addr *)ea->arp_spa;
 	char addr[INET_ADDRSTRLEN];
 	struct ifnet *rifp;
-	unsigned int len;
+	struct mbuf *m;
 	int changed = 0;
 
 	KERNEL_ASSERT_LOCKED();
@@ -672,20 +666,18 @@ arpcache(struct ifnet *ifp, struct ether_arp *ea, struct rtentry *rt)
 
 	la->la_asked = 0;
 	la->la_refreshed = 0;
-	while ((len = ml_len(&la->la_ml)) != 0) {
-		struct mbuf *mh;
+	while ((m = mq_dequeue(&la->la_mq)) != NULL) {
+		unsigned int len;
 
-		mh = ml_dequeue(&la->la_ml);
-		la_hold_total--;
+		atomic_dec_int(&la_hold_total);
+		len = mq_len(&la->la_mq);
 
-		ifp->if_output(ifp, mh, rt_key(rt), rt);
+		ifp->if_output(ifp, m, rt_key(rt), rt);
 
-		if (ml_len(&la->la_ml) == len) {
+		/* XXXSMP we discard if other CPU enqueues */
+		if (mq_len(&la->la_mq) > len) {
 			/* mbuf is back in queue. Discard. */
-			while ((mh = ml_dequeue(&la->la_ml)) != NULL) {
-				la_hold_total--;
-				m_freem(mh);
-			}
+			atomic_sub_int(&la_hold_total, mq_purge(&la->la_mq));
 			break;
 		}
 	}
@@ -699,7 +691,7 @@ arpinvalidate(struct rtentry *rt)
 	struct llinfo_arp *la = (struct llinfo_arp *)rt->rt_llinfo;
 	struct sockaddr_dl *sdl = satosdl(rt->rt_gateway);
 
-	la_hold_total -= ml_purge(&la->la_ml);
+	atomic_sub_int(&la_hold_total, mq_purge(&la->la_mq));
 	sdl->sdl_alen = 0;
 	la->la_asked = 0;
 }
-- 
2.20.1