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, 4 insertions, 0 deletions

diff --git a/sys/netinet/cc/cc_newreno.c b/sys/netinet/cc/cc_newreno.c
index c095540..f26553d 100644
--- a/sys/netinet/cc/cc_newreno.c
+++ b/sys/netinet/cc/cc_newreno.c
@@ -182,6 +182,10 @@ newreno_cong_signal(struct cc_var *ccv, uint32_t type)
 {
 	u_int win;
 
+	/* Catch algos which mistakenly leak private signal types. */
+	KASSERT((type & CC_SIGPRIVMASK) == 0,
+	    ("%s: congestion signal type 0x%08x is private\n", __func__, type));
+
 	win = max(CCV(ccv, snd_cwnd) / 2 / CCV(ccv, t_maxseg), 2) *
 	    CCV(ccv, t_maxseg);