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diff --git a/share/man/man4/tcp.4 b/share/man/man4/tcp.4
--- a/share/man/man4/tcp.4
+++ b/share/man/man4/tcp.4
@@ -34,7 +34,7 @@
.\" From: @(#)tcp.4 8.1 (Berkeley) 6/5/93
.\" $FreeBSD$
.\"
-.Dd February 13, 2021
+.Dd April 8, 2021
.Dt TCP 4
.Os
.Sh NAME
@@ -628,7 +628,6 @@
Enable support for TCP Explicit Congestion Notification (ECN).
ECN allows a TCP sender to reduce the transmission rate in order to
avoid packet drops.
-Settings:
.Bl -tag -compact
.It 0
Disable ECN.
@@ -638,6 +637,7 @@
.It 2
Allow incoming connections to request ECN.
Outgoing connections will not request ECN.
+(default)
.El
.It Va ecn.maxretries
Number of retries (SYN or SYN/ACK retransmits) before disabling ECN on a
@@ -674,6 +674,54 @@
MSS to try for IPv4 if PMTU blackhole detection is turned on.
.It Va v6pmtud_blackhole_mss
MSS to try for IPv6 if PMTU blackhole detection is turned on.
+.It Va hostcache.enable
+The TCP host cache is used to cache connection details and metrics to
+improve future performance of connections between the same hosts.
+At the completion of a TCP connection, a host will cache information
+for the connection for some defined period of time.
+.Bl -tag -compact
+.It 0
+Disable the host cache.
+.It 1
+Enable the host cache. (default)
+.It Va hostcache.purgenow
+Immediately purge all entries once set to any value.
+Setting this to 2 will also reseed the hash salt.
+.It Va hostcache.purge
+Expire all entires on next pruning of host cache entries.
+Any non-zero setting will be reset to zero, once the pruge
+is running.
+.Bl -tag -compact
+.It 0
+Do not purge all entries when pruning the host cache. (default)
+.It 1
+Purge all entries when doing the next pruning.
+.It 2
+Purge all entries, and also reseed the hash salt.
+.It Va hostcache.prune
+Time in seconds between pruning expired host cache entries.
+Defaults to 300 (5 minutes).
+.It Va hostcache.expire
+Time in seconds, how long a entry should be kept in the
+host cache since last accessed.
+Defaults to 3600 (1 hour).
+.It Va hostcache.count
+The current number of entries in the host cache.
+.It Va hostcache.bucketlimit
+The maximum number of entries for the same hash.
+Defaults to 30.
+.It Va hostcache.hashsize
+Size of TCP hostcache hashtable.
+This number has to be a power of two, or will be rejected.
+Defaults to 512.
+.It Va hostcache.cachelimit
+Overall entry limit for hostcache.
+Defaults to hashsize * bucketlimit.
+.It Va hostcache.histo
+Provide a Histogram of the hostcache hash utilization.
+.It Va hostcache.list
+Provide a complete list of all current entries in the host
+cache.
.It Va functions_available
List of available TCP function blocks (TCP stacks).
.It Va functions_default
diff --git a/sys/netinet/tcp_hostcache.c b/sys/netinet/tcp_hostcache.c
--- a/sys/netinet/tcp_hostcache.c
+++ b/sys/netinet/tcp_hostcache.c
@@ -71,6 +71,7 @@
#include <sys/param.h>
#include <sys/systm.h>
+#include <sys/hash.h>
#include <sys/jail.h>
#include <sys/kernel.h>
#include <sys/lock.h>
@@ -127,6 +128,7 @@
uma_zone_t zone;
u_int hashsize;
u_int hashmask;
+ u_int hashsalt;
u_int bucket_limit;
u_int cache_count;
u_int cache_limit;
@@ -210,16 +212,14 @@
static MALLOC_DEFINE(M_HOSTCACHE, "hostcache", "TCP hostcache");
+/* Use jenkins_hash32(), as in other parts of the tcp stack */
#define HOSTCACHE_HASH(ip) \
- (((ip)->s_addr ^ ((ip)->s_addr >> 7) ^ ((ip)->s_addr >> 17)) & \
- V_tcp_hostcache.hashmask)
+ (jenkins_hash32((uint32_t *)(ip), 1, V_tcp_hostcache.hashsalt) & \
+ V_tcp_hostcache.hashmask)
-/* XXX: What is the recommended hash to get good entropy for IPv6 addresses? */
#define HOSTCACHE_HASH6(ip6) \
- (((ip6)->s6_addr32[0] ^ \
- (ip6)->s6_addr32[1] ^ \
- (ip6)->s6_addr32[2] ^ \
- (ip6)->s6_addr32[3]) & \
+ (jenkins_hash32((uint32_t *)&((ip6)->s6_addr32[0]), 4, \
+ V_tcp_hostcache.hashsalt) & \
V_tcp_hostcache.hashmask)
#define THC_LOCK(lp) mtx_lock(lp)
@@ -239,6 +239,7 @@
V_tcp_hostcache.bucket_limit = TCP_HOSTCACHE_BUCKETLIMIT;
V_tcp_hostcache.expire = TCP_HOSTCACHE_EXPIRE;
V_tcp_hostcache.prune = TCP_HOSTCACHE_PRUNE;
+ V_tcp_hostcache.hashsalt = arc4random();
TUNABLE_INT_FETCH("net.inet.tcp.hostcache.hashsize",
&V_tcp_hostcache.hashsize);
@@ -836,6 +837,8 @@
int all = 0;
if (V_tcp_hostcache.purgeall) {
+ if (V_tcp_hostcache.purgeall == 2)
+ V_tcp_hostcache.hashsalt = arc4random();
all = 1;
V_tcp_hostcache.purgeall = 0;
}
@@ -860,6 +863,8 @@
if (error || !req->newptr)
return (error);
+ if (val == 2)
+ V_tcp_hostcache.hashsalt = arc4random();
tcp_hc_purge_internal(1);
callout_reset(&V_tcp_hc_callout, V_tcp_hostcache.prune * hz,

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