- Add some helper hook points to the TCP stack. The hooks allow Khelp modules to

  access inbound/outbound events and associated data for established TCP
  connections. The hooks only run if at least one hook function is registered
  for the hook point, ensuring the impact on the stack is effectively nil when
  no TCP Khelp modules are loaded. struct tcp_hhook_data is passed as contextual
  data to any registered Khelp module hook functions.

- Add an OSD (Object Specific Data) pointer to struct tcpcb to allow Khelp
  modules to associate per-connection data with the TCP control block.

- Bump __FreeBSD_version and add a note to UPDATING regarding to ABI changes
  introduced by this commit and r216753.

In collaboration with:	David Hayes <dahayes at swin edu au> and
				Grenville Armitage <garmitage at swin edu au>
Sponsored by:	FreeBSD Foundation
Reviewed by:	bz, others along the way
MFC after:	3 months

1 files changed, 20 insertions, 0 deletions

diff --git a/sys/netinet/tcp_var.h b/sys/netinet/tcp_var.h
index 3305b1a..4a43213 100644
--- a/sys/netinet/tcp_var.h
+++ b/sys/netinet/tcp_var.h
@@ -201,6 +201,7 @@ struct tcpcb {
 	int	t_bytes_acked;		/* # bytes acked during current RTT */
 	struct cc_algo	*cc_algo;	/* congestion control algorithm */
 	struct cc_var	*ccv;
+	struct osd	*osd;		/* storage for Khelp module data */
 
 	int	t_ispare;		/* explicit pad for 64bit alignment */
 	void	*t_pspare2[4];		/* 4 TBD */
@@ -501,6 +502,22 @@ struct	tcpstat {
 void	kmod_tcpstat_inc(int statnum);
 #define	KMOD_TCPSTAT_INC(name)						\
 	kmod_tcpstat_inc(offsetof(struct tcpstat, name) / sizeof(u_long))
+
+/*
+ * TCP specific helper hook point identifiers.
+ */
+#define	HHOOK_TCP_EST_IN		0
+#define	HHOOK_TCP_EST_OUT		1
+#define	HHOOK_TCP_LAST			HHOOK_TCP_EST_OUT
+
+struct tcp_hhook_data {
+	struct tcpcb *tp;
+	struct tcphdr *th;
+	struct tcpopt *to;
+	long len;
+	int tso;
+	tcp_seq  curack;
+};
 #endif
 
 /*
@@ -608,6 +625,9 @@ VNET_DECLARE(int, tcp_ecn_maxretries);
 #define	V_tcp_do_ecn		VNET(tcp_do_ecn)
 #define	V_tcp_ecn_maxretries	VNET(tcp_ecn_maxretries)
 
+VNET_DECLARE(struct hhook_head *, tcp_hhh[HHOOK_TCP_LAST+1]);
+#define	V_tcp_hhh		VNET(tcp_hhh)
+
 int	 tcp_addoptions(struct tcpopt *, u_char *);
 int	 tcp_ccalgounload(struct cc_algo *unload_algo);
 struct tcpcb *