From 8a56c645335e50e7e63cc47cf00ea631030533c8 Mon Sep 17 00:00:00 2001 From: Hiren Panchasara Date: Fri, 30 Sep 2016 00:10:57 +0000 Subject: [PATCH] This adds a sysctl which allows you to disable the TCP hostcache. This is handy during testing of network related changes where cached entries may pollute your results, or during known congestion events where you don't want to unfairly penalize hosts. Prior to r232346 this would have meant you would break any connection with a sub 1500 MTU, as the hostcache was authoritative. All entries as they stand today should simply be used to pre populate values for efficiency. Submitted by: Jason Wolfe (j at nitrology dot com) Reviewed by: rwatson, sbruno, rrs , bz (earlier version) MFC after: 2 weeks Sponsored by: Limelight Networks Differential Revision: https://reviews.freebsd.org/D6198 --- sys/netinet/tcp_hostcache.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/sys/netinet/tcp_hostcache.c b/sys/netinet/tcp_hostcache.c index 5e8342f401d..848c9226ab6 100644 --- a/sys/netinet/tcp_hostcache.c +++ b/sys/netinet/tcp_hostcache.c @@ -124,6 +124,12 @@ static void tcp_hc_purge(void *); static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, hostcache, CTLFLAG_RW, 0, "TCP Host cache"); +VNET_DEFINE(int, tcp_use_hostcache) = 1; +#define V_tcp_use_hostcache VNET(tcp_use_hostcache) +SYSCTL_INT(_net_inet_tcp_hostcache, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW, + &VNET_NAME(tcp_use_hostcache), 0, + "Enable the TCP hostcache"); + SYSCTL_UINT(_net_inet_tcp_hostcache, OID_AUTO, cachelimit, CTLFLAG_VNET | CTLFLAG_RDTUN, &VNET_NAME(tcp_hostcache.cache_limit), 0, "Overall entry limit for hostcache"); @@ -276,6 +282,9 @@ tcp_hc_lookup(struct in_conninfo *inc) struct hc_head *hc_head; struct hc_metrics *hc_entry; + if (!V_tcp_use_hostcache) + return NULL; + KASSERT(inc != NULL, ("tcp_hc_lookup with NULL in_conninfo pointer")); /* @@ -332,6 +341,9 @@ tcp_hc_insert(struct in_conninfo *inc) struct hc_head *hc_head; struct hc_metrics *hc_entry; + if (!V_tcp_use_hostcache) + return NULL; + KASSERT(inc != NULL, ("tcp_hc_insert with NULL in_conninfo pointer")); /* @@ -421,6 +433,9 @@ tcp_hc_get(struct in_conninfo *inc, struct hc_metrics_lite *hc_metrics_lite) { struct hc_metrics *hc_entry; + if (!V_tcp_use_hostcache) + return; + /* * Find the right bucket. */ @@ -452,7 +467,7 @@ tcp_hc_get(struct in_conninfo *inc, struct hc_metrics_lite *hc_metrics_lite) /* * External function: look up an entry in the hostcache and return the - * discovered path MTU. Returns NULL if no entry is found or value is not + * discovered path MTU. Returns 0 if no entry is found or value is not * set. */ u_long @@ -461,6 +476,9 @@ tcp_hc_getmtu(struct in_conninfo *inc) struct hc_metrics *hc_entry; u_long mtu; + if (!V_tcp_use_hostcache) + return 0; + hc_entry = tcp_hc_lookup(inc); if (hc_entry == NULL) { return 0; @@ -482,6 +500,9 @@ tcp_hc_updatemtu(struct in_conninfo *inc, u_long mtu) { struct hc_metrics *hc_entry; + if (!V_tcp_use_hostcache) + return; + /* * Find the right bucket. */ @@ -521,6 +542,9 @@ tcp_hc_update(struct in_conninfo *inc, struct hc_metrics_lite *hcml) { struct hc_metrics *hc_entry; + if (!V_tcp_use_hostcache) + return; + hc_entry = tcp_hc_lookup(inc); if (hc_entry == NULL) { hc_entry = tcp_hc_insert(inc);