Algorithm modules can define their own private congestion signal types in the

top 8 bits of the 32 bit signal bit field space for internal use. These private
signals should not be leaked outside of a module.

Given that many algorithm modules use the NewReno hook functions to simplify
their implementation, the obvious place such a leak would show up is in the
NewReno cong_signal hook function.

- Show the full number of significant bits in the signal type definitions in
  <netinet/cc.h>.

- Add a bitmask to simplify figuring out if a given signal is in the private or
  public bit range.

- Add a sanity check in newreno_cong_signal() to ensure private signals are not
  being leaked into the hook function.

Sponsored by:	FreeBSD Foundation
Discussed with:	David Hayes <dahayes at swin edu au>
MFC after:	1 week
X-MFC with:	r215166

1 files changed, 6 insertions, 4 deletions

diff --git a/sys/netinet/cc.h b/sys/netinet/cc.h
index aaa1d67..332e51c 100644
--- a/sys/netinet/cc.h
+++ b/sys/netinet/cc.h
@@ -101,10 +101,12 @@ struct cc_var {
  * bits (0x01000000 - 0x80000000) are reserved for CC algos to declare their own
  * congestion signal types.
  */
-#define	CC_ECN		0x000001/* ECN marked packet received. */
-#define	CC_RTO		0x000002/* RTO fired. */
-#define	CC_RTO_ERR	0x000004/* RTO fired in error. */
-#define	CC_NDUPACK	0x000008/* Threshold of dupack's reached. */
+#define	CC_ECN		0x00000001	/* ECN marked packet received. */
+#define	CC_RTO		0x00000002	/* RTO fired. */
+#define	CC_RTO_ERR	0x00000004	/* RTO fired in error. */
+#define	CC_NDUPACK	0x00000008	/* Threshold of dupack's reached. */
+
+#define	CC_SIGPRIVMASK	0xFF000000	/* Mask to check if sig is private. */
 
 /*
  * Structure to hold data and function pointers that together represent a