Index: sys/kern/kern_jail.c
===================================================================
--- sys/kern/kern_jail.c
+++ sys/kern/kern_jail.c
@@ -2510,14 +2510,14 @@
  * PR_IP4 and PR_IP6), or only the single bit is examined, without regard
  * to any other prison data.
  */
-int
+bool
 prison_flag(struct ucred *cred, unsigned flag)
 {
 
 	return (cred->cr_prison->pr_flags & flag);
 }
 
-int
+bool
 prison_allow(struct ucred *cred, unsigned flag)
 {
 
@@ -3141,16 +3141,16 @@
 }
 
 /*
- * Return 1 if p2 is a child of p1, otherwise 0.
+ * Return true if p2 is a child of p1, otherwise false.
  */
-int
+bool
 prison_ischild(struct prison *pr1, struct prison *pr2)
 {
 
 	for (pr2 = pr2->pr_parent; pr2 != NULL; pr2 = pr2->pr_parent)
 		if (pr1 == pr2)
-			return (1);
-	return (0);
+			return (true);
+	return (false);
 }
 
 /*
@@ -3185,21 +3185,21 @@
 }
 
 /*
- * Return 1 if the passed credential is in a jail and that jail does not
- * have its own virtual network stack, otherwise 0.
+ * Return true if the passed credential is in a jail and that jail does not
+ * have its own virtual network stack, otherwise false.
  */
-int
+bool
 jailed_without_vnet(struct ucred *cred)
 {
 
 	if (!jailed(cred))
-		return (0);
+		return (false);
 #ifdef VIMAGE
 	if (prison_owns_vnet(cred))
-		return (0);
+		return (false);
 #endif
 
-	return (1);
+	return (true);
 }
 
 /*
@@ -3261,9 +3261,9 @@
  * Determine whether the prison represented by cred owns
  * its vnet rather than having it inherited.
  *
- * Returns 1 in case the prison owns the vnet, 0 otherwise.
+ * Returns true in case the prison owns the vnet, false otherwise.
  */
-int
+bool
 prison_owns_vnet(struct ucred *cred)
 {
 
@@ -3271,7 +3271,7 @@
 	 * vnets cannot be added/removed after jail creation,
 	 * so no need to lock here.
 	 */
-	return (cred->cr_prison->pr_flags & PR_VNET ? 1 : 0);
+	return ((cred->cr_prison->pr_flags & PR_VNET) != 0);
 }
 #endif
 
Index: sys/netinet/in_jail.c
===================================================================
--- sys/netinet/in_jail.c
+++ sys/netinet/in_jail.c
@@ -94,10 +94,11 @@
  * Restrict a prison's IP address list with its parent's, possibly replacing
  * it.  Return true if the replacement buffer was used (or would have been).
  */
-int
+bool
 prison_restrict_ip4(struct prison *pr, struct in_addr *newip4)
 {
-	int ii, ij, used;
+	int ii, ij;
+	bool used;
 	struct prison *ppr;
 
 	ppr = pr->pr_parent;
@@ -110,12 +111,12 @@
 			 * (if it was passed).  If there's no buffer, try to
 			 * allocate one.
 			 */
-			used = 1;
+			used = true;
 			if (newip4 == NULL) {
 				newip4 = malloc(ppr->pr_ip4s * sizeof(*newip4),
 				    M_PRISON, M_NOWAIT);
 				if (newip4 != NULL)
-					used = 0;
+					used = false;
 			}
 			if (newip4 != NULL) {
 				bcopy(ppr->pr_ip4, newip4,
@@ -171,7 +172,7 @@
 			pr->pr_ip4 = NULL;
 		}
 	}
-	return (0);
+	return (false);
 }
 
 /*
@@ -210,49 +211,47 @@
 }
 
 /*
- * Return 1 if we should do proper source address selection or are not jailed.
- * We will return 0 if we should bypass source address selection in favour
+ * Return true if we should do proper source address selection or are not jailed.
+ * We will return false if we should bypass source address selection in favour
  * of the primary jail IPv4 address. Only in this case *ia will be updated and
  * returned in NBO.
- * Return EAFNOSUPPORT, in case this jail does not allow IPv4.
+ * Return true, even in case this jail does not allow IPv4.
  */
-int
+bool
 prison_saddrsel_ip4(struct ucred *cred, struct in_addr *ia)
 {
 	struct prison *pr;
 	struct in_addr lia;
-	int error;
 
 	KASSERT(cred != NULL, ("%s: cred is NULL", __func__));
 	KASSERT(ia != NULL, ("%s: ia is NULL", __func__));
 
 	if (!jailed(cred))
-		return (1);
+		return (true);
 
 	pr = cred->cr_prison;
 	if (pr->pr_flags & PR_IP4_SADDRSEL)
-		return (1);
+		return (true);
 
 	lia.s_addr = INADDR_ANY;
-	error = prison_get_ip4(cred, &lia);
-	if (error)
-		return (error);
+	if (prison_get_ip4(cred, &lia))
+		return (true);
 	if (lia.s_addr == INADDR_ANY)
-		return (1);
+		return (true);
 
 	ia->s_addr = lia.s_addr;
-	return (0);
+	return (false);
 }
 
 /*
  * Return true if pr1 and pr2 have the same IPv4 address restrictions.
  */
-int
+bool
 prison_equal_ip4(struct prison *pr1, struct prison *pr2)
 {
 
 	if (pr1 == pr2)
-		return (1);
+		return (true);
 
 	/*
 	 * No need to lock since the PR_IP4_USER flag can't be altered for
Index: sys/netinet6/in6_jail.c
===================================================================
--- sys/netinet6/in6_jail.c
+++ sys/netinet6/in6_jail.c
@@ -84,10 +84,15 @@
 	return (rc);
 }
 
-int
+/*
+ * Restrict a prison's IP address list with its parent's, possibly replacing
+ * it.  Return true if the replacement buffer was used (or would have been).
+ */
+bool
 prison_restrict_ip6(struct prison *pr, struct in6_addr *newip6)
 {
-	int ii, ij, used;
+	int ii, ij;
+	bool used;
 	struct prison *ppr;
 
 	ppr = pr->pr_parent;
@@ -100,12 +105,12 @@
 			 * (if it was passed).  If there's no buffer, try to
 			 * allocate one.
 			 */
-			used = 1;
+			used = true;
 			if (newip6 == NULL) {
 				newip6 = malloc(ppr->pr_ip6s * sizeof(*newip6),
 				    M_PRISON, M_NOWAIT);
 				if (newip6 != NULL)
-					used = 0;
+					used = false;
 			}
 			if (newip6 != NULL) {
 				bcopy(ppr->pr_ip6, newip6,
@@ -163,7 +168,7 @@
 			pr->pr_ip6 = NULL;
 		}
 	}
-	return 0;
+	return (false);
 }
 
 /*
@@ -201,49 +206,47 @@
 }
 
 /*
- * Return 1 if we should do proper source address selection or are not jailed.
- * We will return 0 if we should bypass source address selection in favour
+ * Return true if we should do proper source address selection or are not jailed.
+ * We will return false if we should bypass source address selection in favour
  * of the primary jail IPv6 address. Only in this case *ia will be updated and
  * returned in NBO.
- * Return EAFNOSUPPORT, in case this jail does not allow IPv6.
+ * Return true, even in case this jail does not allow IPv6.
  */
-int
+bool
 prison_saddrsel_ip6(struct ucred *cred, struct in6_addr *ia6)
 {
 	struct prison *pr;
 	struct in6_addr lia6;
-	int error;
 
 	KASSERT(cred != NULL, ("%s: cred is NULL", __func__));
 	KASSERT(ia6 != NULL, ("%s: ia6 is NULL", __func__));
 
 	if (!jailed(cred))
-		return (1);
+		return (true);
 
 	pr = cred->cr_prison;
 	if (pr->pr_flags & PR_IP6_SADDRSEL)
-		return (1);
+		return (true);
 
 	lia6 = in6addr_any;
-	error = prison_get_ip6(cred, &lia6);
-	if (error)
-		return (error);
+  if (prison_get_ip6(cred, &lia6))
+		return (true);
 	if (IN6_IS_ADDR_UNSPECIFIED(&lia6))
-		return (1);
+		return (true);
 
 	bcopy(&lia6, ia6, sizeof(struct in6_addr));
-	return (0);
+	return (false);
 }
 
 /*
  * Return true if pr1 and pr2 have the same IPv6 address restrictions.
  */
-int
+bool
 prison_equal_ip6(struct prison *pr1, struct prison *pr2)
 {
 
 	if (pr1 == pr2)
-		return (1);
+		return (true);
 
 	while (pr1 != &prison0 &&
 #ifdef VIMAGE
Index: sys/sys/jail.h
===================================================================
--- sys/sys/jail.h
+++ sys/sys/jail.h
@@ -404,23 +404,23 @@
  */
 #define jailed(cred)	(cred->cr_prison != &prison0)
 
-int jailed_without_vnet(struct ucred *);
+bool jailed_without_vnet(struct ucred *);
 void getcredhostname(struct ucred *, char *, size_t);
 void getcreddomainname(struct ucred *, char *, size_t);
 void getcredhostuuid(struct ucred *, char *, size_t);
 void getcredhostid(struct ucred *, unsigned long *);
 void getjailname(struct ucred *cred, char *name, size_t len);
 void prison0_init(void);
-int prison_allow(struct ucred *, unsigned);
+bool prison_allow(struct ucred *, unsigned);
 int prison_check(struct ucred *cred1, struct ucred *cred2);
-int prison_owns_vnet(struct ucred *);
+bool prison_owns_vnet(struct ucred *);
 int prison_canseemount(struct ucred *cred, struct mount *mp);
 void prison_enforce_statfs(struct ucred *cred, struct mount *mp,
     struct statfs *sp);
 struct prison *prison_find(int prid);
 struct prison *prison_find_child(struct prison *, int);
 struct prison *prison_find_name(struct prison *, const char *);
-int prison_flag(struct ucred *, unsigned);
+bool prison_flag(struct ucred *, unsigned);
 void prison_free(struct prison *pr);
 void prison_free_locked(struct prison *pr);
 void prison_hold(struct prison *pr);
@@ -428,27 +428,27 @@
 void prison_proc_hold(struct prison *);
 void prison_proc_free(struct prison *);
 void prison_set_allow(struct ucred *cred, unsigned flag, int enable);
-int prison_ischild(struct prison *, struct prison *);
+bool prison_ischild(struct prison *, struct prison *);
 bool prison_isalive(struct prison *);
 bool prison_isvalid(struct prison *);
-int prison_equal_ip4(struct prison *, struct prison *);
+bool prison_equal_ip4(struct prison *, struct prison *);
 int prison_get_ip4(struct ucred *cred, struct in_addr *ia);
 int prison_local_ip4(struct ucred *cred, struct in_addr *ia);
 int prison_remote_ip4(struct ucred *cred, struct in_addr *ia);
 int prison_check_ip4(const struct ucred *, const struct in_addr *);
 int prison_check_ip4_locked(const struct prison *, const struct in_addr *);
-int prison_saddrsel_ip4(struct ucred *, struct in_addr *);
-int prison_restrict_ip4(struct prison *, struct in_addr *);
+bool prison_saddrsel_ip4(struct ucred *, struct in_addr *);
+bool prison_restrict_ip4(struct prison *, struct in_addr *);
 int prison_qcmp_v4(const void *, const void *);
 #ifdef INET6
-int prison_equal_ip6(struct prison *, struct prison *);
+bool prison_equal_ip6(struct prison *, struct prison *);
 int prison_get_ip6(struct ucred *, struct in6_addr *);
 int prison_local_ip6(struct ucred *, struct in6_addr *, int);
 int prison_remote_ip6(struct ucred *, struct in6_addr *);
 int prison_check_ip6(const struct ucred *, const struct in6_addr *);
 int prison_check_ip6_locked(const struct prison *, const struct in6_addr *);
-int prison_saddrsel_ip6(struct ucred *, struct in6_addr *);
-int prison_restrict_ip6(struct prison *, struct in6_addr *);
+bool prison_saddrsel_ip6(struct ucred *, struct in6_addr *);
+bool prison_restrict_ip6(struct prison *, struct in6_addr *);
 int prison_qcmp_v6(const void *, const void *);
 #endif
 int prison_check_af(struct ucred *cred, int af);