On CC algorithm module unload, we walk the list of active TCP control blocks.

Any found to be using the algorithm that is about to go away are switched back
to NewReno to avoid leaving dangling pointers which would trigger a panic. For
VIMAGE kernels, there is a list per vnet to walk, yet the implementation was
only examining one of the vnet lists.

Fix the implementation of the above feature for VIMAGE kernels by looping
through all active TCP control blocks across all vnets.

Sponsored by:	FreeBSD Foundation
Tested by:	Mikolaj Golub <to.my.trociny at gmail com>
Reviewed by:	bz (briefly)
MFC after:	11 weeks

1 files changed, 35 insertions, 24 deletions

diff --git a/sys/netinet/cc/cc.c b/sys/netinet/cc/cc.c
index de83aaf..f346078 100644
--- a/sys/netinet/cc/cc.c
+++ b/sys/netinet/cc/cc.c
@@ -193,6 +193,7 @@ cc_deregister_algo(struct cc_algo *remove_cc)
 	struct tcpcb *tp;
 	struct inpcb *inp;
 	int err;
+	VNET_ITERATOR_DECL(vnet_iter);
 
 	err = ENOENT;
 
@@ -221,9 +222,10 @@ cc_deregister_algo(struct cc_algo *remove_cc)
 	
 	if (!err) {
 		/*
-		 * Check all active control blocks and change any that are
-		 * using this algorithm back to newreno. If the algorithm that
-		 * was in use requires cleanup code to be run, call it.
+		 * Check all active control blocks across all network stacks and
+		 * change any that are using this algorithm back to newreno. If
+		 * the algorithm that was in use requires cleanup code to be
+		 * run, call it.
 		 *
 		 * New connections already part way through being initialised
 		 * with the CC algo we're removing will not race with this code
@@ -231,30 +233,39 @@ cc_deregister_algo(struct cc_algo *remove_cc)
 		 * We therefore don't enter the loop below until the connection
 		 * list has stabilised.
 		 */
-		INP_INFO_RLOCK(&V_tcbinfo);
-		LIST_FOREACH(inp, &V_tcb, inp_list) {
-			INP_WLOCK(inp);
-			/* Important to skip tcptw structs. */
-			if (!(inp->inp_flags & INP_TIMEWAIT) &&
-			    (tp = intotcpcb(inp)) != NULL) {
-				/*
-				 * By holding INP_WLOCK here, we are
-				 * assured that the connection is not
-				 * currently executing inside the CC
-				 * module's functions i.e. it is safe to
-				 * make the switch back to newreno.
-				 */
-				if (CC_ALGO(tp) == remove_cc) {
-					tmpfuncs = CC_ALGO(tp);
-					/* Newreno does not require any init. */
-					CC_ALGO(tp) = &newreno_cc_algo;
-					if (tmpfuncs->cb_destroy != NULL)
-						tmpfuncs->cb_destroy(tp->ccv);
+		VNET_LIST_RLOCK();
+		VNET_FOREACH(vnet_iter) {
+			CURVNET_SET(vnet_iter);
+			INP_INFO_RLOCK(&V_tcbinfo);
+			LIST_FOREACH(inp, &V_tcb, inp_list) {
+				INP_WLOCK(inp);
+				/* Important to skip tcptw structs. */
+				if (!(inp->inp_flags & INP_TIMEWAIT) &&
+				    (tp = intotcpcb(inp)) != NULL) {
+					/*
+					 * By holding INP_WLOCK here, we are
+					 * assured that the connection is not
+					 * currently executing inside the CC
+					 * module's functions i.e. it is safe
+					 * to make the switch back to newreno.
+					 */
+					if (CC_ALGO(tp) == remove_cc) {
+						tmpfuncs = CC_ALGO(tp);
+						/*
+						 * Newreno does not
+						 * require any init.
+						 */
+						CC_ALGO(tp) = &newreno_cc_algo;
+						if (tmpfuncs->cb_destroy != NULL)
+							tmpfuncs->cb_destroy(tp->ccv);
+					}
 				}
+				INP_WUNLOCK(inp);
 			}
-			INP_WUNLOCK(inp);
+			INP_INFO_RUNLOCK(&V_tcbinfo);
+			CURVNET_RESTORE();
 		}
-		INP_INFO_RUNLOCK(&V_tcbinfo);
+		VNET_LIST_RUNLOCK();
 	}
 
 	return (err);