libalias: Switch to efficient data structure for outgoing traffic

Current data structure is using a hash of unordered lists.  Those
unordered lists are quite efficient, because the least recently
inserted entries are most likely to be used again.  In order to avoid
long search times in other cases, the lists are hashed into many
buckets.  Unfortunatly a search for a miss needs an exhaustive
inspection and a careful definition of the hash.

Splay trees offer a similar feature - almost O(1) for access of the
least recently used entries), and amortized O(ln(n) - for almost all
other cases.  Get rid of the hash.

Discussed with:	Dimitry Luhtionov
MFC after:	1 week
Differential Revision: https://reviews.freebsd.org/D30516

2 files changed, 36 insertions, 49 deletions

diff --git a/sys/netinet/libalias/alias_db.c b/sys/netinet/libalias/alias_db.c
index c5ecc49ed191..a5a21e40d0cf 100644
--- a/sys/netinet/libalias/alias_db.c
+++ b/sys/netinet/libalias/alias_db.c
@@ -324,11 +324,11 @@ struct alias_link {
 	/* Linked list of pointers for input and output lookup tables  */
 	union {
 		struct {
-			LIST_ENTRY(alias_link) in;
-			LIST_ENTRY(alias_link) out;
+			SPLAY_ENTRY(alias_link) out;
+			LIST_ENTRY (alias_link) in;
 		} all;
 		struct {
-			LIST_ENTRY(alias_link) list;
+			LIST_ENTRY (alias_link) list;
 		} pptp;
 	};
 	struct {
@@ -389,8 +389,6 @@ Miscellaneous:
 /* Local prototypes */
 static struct group_in *
 StartPointIn(struct libalias *, struct in_addr, u_short, int, int);
-static u_int
-StartPointOut(struct in_addr, struct in_addr, u_short, u_short, int);
 static int	SeqDiff(u_long, u_long);
 
 #ifndef NO_FW_PUNCH
@@ -408,6 +406,24 @@ static void	UninitPacketAliasLog(struct libalias *);
 
 void		SctpShowAliasStats(struct libalias *la);
 
+
+/* Splay handling */
+static inline int
+cmp_out(struct alias_link *a, struct alias_link *b) {
+	int i = a->src_port - b->src_port;
+	if (i != 0) return (i);
+	i = a->src_addr.s_addr - b->src_addr.s_addr;
+	if (i != 0) return (i);
+	i = a->dst_addr.s_addr - b->dst_addr.s_addr;
+	if (i != 0) return (i);
+	i = a->dst_port - b->dst_port;
+	if (i != 0) return (i);
+	i = a->link_type - b->link_type;
+	return (i);
+}
+SPLAY_PROTOTYPE(splay_out, alias_link, all.out, cmp_out);
+SPLAY_GENERATE(splay_out, alias_link, all.out, cmp_out);
+
 #define INGUARD						\
    if (grp->alias_port != alias_port ||			\
        grp->link_type != link_type ||			\
@@ -449,21 +465,6 @@ StartPointIn(struct libalias *la,
 }
 #undef INGUARD
 
-static u_int
-StartPointOut(struct in_addr src_addr, struct in_addr dst_addr,
-    u_short src_port, u_short dst_port, int link_type)
-{
-	u_int n;
-
-	n = src_addr.s_addr;
-	n += dst_addr.s_addr;
-	n += src_port;
-	n += dst_port;
-	n += link_type;
-
-	return (n % LINK_TABLE_OUT_SIZE);
-}
-
 static int
 SeqDiff(u_long x, u_long y)
 {
@@ -893,7 +894,7 @@ DeleteLink(struct alias_link **plnk, int deletePermanent)
 			} while ((curr = next) != head);
 		} else {
 			/* Adjust output table pointers */
-			LIST_REMOVE(lnk, all.out);
+			SPLAY_REMOVE(splay_out, &la->linkSplayOut, lnk);
 		}
 
 		/* Adjust input table pointers */
@@ -956,7 +957,6 @@ AddLink(struct libalias *la, struct in_addr src_addr, struct in_addr dst_addr,
     struct in_addr alias_addr, u_short src_port, u_short dst_port,
     int alias_port_param, int link_type)
 {
-	u_int start_point;
 	struct alias_link *lnk;
 
 	LIBALIAS_LOCK_ASSERT(la);
@@ -1085,9 +1085,7 @@ AddLink(struct libalias *la, struct in_addr src_addr, struct in_addr dst_addr,
 		}
 
 		/* Set up pointers for output lookup table */
-		start_point = StartPointOut(src_addr, dst_addr,
-		    src_port, dst_port, link_type);
-		LIST_INSERT_HEAD(&la->linkTableOut[start_point], lnk, all.out);
+		SPLAY_INSERT(splay_out, &la->linkSplayOut, lnk);
 
 		/* Set up pointers for input lookup table */
 		if (lnk->flags & LINK_PARTIALLY_SPECIFIED)
@@ -1140,35 +1138,25 @@ ReLink(struct alias_link *old_lnk,
 	return (new_lnk);
 }
 
-
-#define OUTGUARD					\
-   if (lnk->src_port != src_port ||			\
-       lnk->src_addr.s_addr != src_addr.s_addr ||	\
-       lnk->dst_addr.s_addr != dst_addr.s_addr ||	\
-       lnk->dst_port != dst_port ||			\
-       lnk->link_type != link_type)			\
-	   continue;
-
 static struct alias_link *
 _SearchLinkOut(struct libalias *la, struct in_addr src_addr,
     struct in_addr dst_addr,
     u_short src_port,
     u_short dst_port,
     int link_type) {
-	u_int i;
 	struct alias_link *lnk;
+	struct alias_link needle = {
+		.src_addr = src_addr,
+		.dst_addr = dst_addr,
+		.src_port = src_port,
+		.dst_port = dst_port,
+		.link_type = link_type
+	};
 
-	i = StartPointOut(src_addr, dst_addr, src_port, dst_port, link_type);
-	LIST_FOREACH(lnk, &la->linkTableOut[i], all.out) {
-		OUTGUARD;
-		return (UseLink(la, lnk));
-	}
-
-	return (NULL);
+	lnk = SPLAY_FIND(splay_out, &la->linkSplayOut, &needle);
+	return (UseLink(la, lnk));
 }
 
-#undef OUTGUARD
-
 static struct alias_link *
 _FindLinkOut(struct libalias *la, struct in_addr src_addr,
     struct in_addr dst_addr,
@@ -2333,7 +2321,7 @@ LibAliasAddServer(struct libalias *la, struct alias_link *lnk, struct in_addr ad
 		if (head == NULL) {
 			server->next = server;
 			/* not usable for outgoing connections */
-			LIST_REMOVE(lnk, all.out);
+			SPLAY_REMOVE(splay_out, &la->linkSplayOut, lnk);
 		} else {
 			struct server *s;
 
@@ -2502,8 +2490,7 @@ LibAliasInit(struct libalias *la)
 		LibAliasTime = time(NULL);
 #endif
 
-		for (i = 0; i < LINK_TABLE_OUT_SIZE; i++)
-			LIST_INIT(&la->linkTableOut[i]);
+		SPLAY_INIT(&la->linkSplayOut);
 		for (i = 0; i < LINK_TABLE_IN_SIZE; i++)
 			LIST_INIT(&la->groupTableIn[i]);
 		LIST_INIT(&la->pptpList);
diff --git a/sys/netinet/libalias/alias_local.h b/sys/netinet/libalias/alias_local.h
index 5628adac203e..a1ad08a979d2 100644
--- a/sys/netinet/libalias/alias_local.h
+++ b/sys/netinet/libalias/alias_local.h
@@ -48,6 +48,7 @@
 #ifndef _ALIAS_LOCAL_H_
 #define	_ALIAS_LOCAL_H_
 
+#include <sys/tree.h>
 #include <sys/types.h>
 #include <sys/sysctl.h>
 
@@ -66,7 +67,6 @@
 #endif
 
 /* Sizes of input and output link tables */
-#define LINK_TABLE_OUT_SIZE	4001
 #define LINK_TABLE_IN_SIZE	4001
 
 #define	GET_ALIAS_PORT		-1
@@ -100,7 +100,7 @@ struct libalias {
 	/* Lookup table of pointers to chains of link records.
 	 * Each link record is doubly indexed into input and
 	 * output lookup tables. */
-	LIST_HEAD (, alias_link) linkTableOut[LINK_TABLE_OUT_SIZE];
+	SPLAY_HEAD(splay_out, alias_link) linkSplayOut;
 	LIST_HEAD (, group_in)   groupTableIn[LINK_TABLE_IN_SIZE];
 	LIST_HEAD (, alias_link) pptpList;
 	/* HouseKeeping */