From f5b0a8743601a4477419171f5046bd07d1c080a0 Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Thu, 19 Jul 2012 12:31:33 -0700 Subject: net: Document dst->obsolete better. Add a big comment explaining how the field works, and use defines instead of magic constants for the values assigned to it. Suggested by Joe Perches. Signed-off-by: David S. Miller diff --git a/include/net/dst.h b/include/net/dst.h index 5161046..0df661a 100644 --- a/include/net/dst.h +++ b/include/net/dst.h @@ -65,7 +65,19 @@ struct dst_entry { unsigned short pending_confirm; short error; + + /* A non-zero value of dst->obsolete forces by-hand validation + * of the route entry. Positive values are set by the generic + * dst layer to indicate that the entry has been forcefully + * destroyed. + * + * Negative values are used by the implementation layer code to + * force invocation of the dst_ops->check() method. + */ short obsolete; +#define DST_OBSOLETE_NONE 0 +#define DST_OBSOLETE_DEAD 2 +#define DST_OBSOLETE_FORCE_CHK -1 unsigned short header_len; /* more space at head required */ unsigned short trailer_len; /* space to reserve at tail */ #ifdef CONFIG_IP_ROUTE_CLASSID @@ -359,7 +371,7 @@ extern struct dst_entry *dst_destroy(struct dst_entry *dst); static inline void dst_free(struct dst_entry *dst) { - if (dst->obsolete > 1) + if (dst->obsolete > 0) return; if (!atomic_read(&dst->__refcnt)) { dst = dst_destroy(dst); diff --git a/net/core/dst.c b/net/core/dst.c index 07bacff..069d51d 100644 --- a/net/core/dst.c +++ b/net/core/dst.c @@ -94,7 +94,7 @@ loop: * But we do not have state "obsoleted, but * referenced by parent", so it is right. */ - if (dst->obsolete > 1) + if (dst->obsolete > 0) continue; ___dst_free(dst); @@ -202,7 +202,7 @@ static void ___dst_free(struct dst_entry *dst) */ if (dst->dev == NULL || !(dst->dev->flags&IFF_UP)) dst->input = dst->output = dst_discard; - dst->obsolete = 2; + dst->obsolete = DST_OBSOLETE_DEAD; } void __dst_free(struct dst_entry *dst) diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c index 47de90d..23cc11d 100644 --- a/net/decnet/dn_route.c +++ b/net/decnet/dn_route.c @@ -1176,7 +1176,7 @@ make_route: if (dev_out->flags & IFF_LOOPBACK) flags |= RTCF_LOCAL; - rt = dst_alloc(&dn_dst_ops, dev_out, 1, 0, DST_HOST); + rt = dst_alloc(&dn_dst_ops, dev_out, 1, DST_OBSOLETE_NONE, DST_HOST); if (rt == NULL) goto e_nobufs; @@ -1444,7 +1444,7 @@ static int dn_route_input_slow(struct sk_buff *skb) } make_route: - rt = dst_alloc(&dn_dst_ops, out_dev, 0, 0, DST_HOST); + rt = dst_alloc(&dn_dst_ops, out_dev, 0, DST_OBSOLETE_NONE, DST_HOST); if (rt == NULL) goto e_nobufs; diff --git a/net/ipv4/route.c b/net/ipv4/route.c index d1d5796..50d2498 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -1221,7 +1221,7 @@ static void rt_set_nexthop(struct rtable *rt, const struct flowi4 *fl4, static struct rtable *rt_dst_alloc(struct net_device *dev, bool nopolicy, bool noxfrm) { - return dst_alloc(&ipv4_dst_ops, dev, 1, -1, + return dst_alloc(&ipv4_dst_ops, dev, 1, DST_OBSOLETE_FORCE_CHK, DST_HOST | DST_NOCACHE | (nopolicy ? DST_NOPOLICY : 0) | (noxfrm ? DST_NOXFRM : 0)); @@ -1969,9 +1969,10 @@ static struct dst_ops ipv4_dst_blackhole_ops = { struct dst_entry *ipv4_blackhole_route(struct net *net, struct dst_entry *dst_orig) { - struct rtable *rt = dst_alloc(&ipv4_dst_blackhole_ops, NULL, 1, 0, 0); struct rtable *ort = (struct rtable *) dst_orig; + struct rtable *rt; + rt = dst_alloc(&ipv4_dst_blackhole_ops, NULL, 1, DST_OBSOLETE_NONE, 0); if (rt) { struct dst_entry *new = &rt->dst; diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 84f6564d..cf02cb9 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -281,7 +281,7 @@ static inline struct rt6_info *ip6_dst_alloc(struct net *net, struct fib6_table *table) { struct rt6_info *rt = dst_alloc(&net->ipv6.ip6_dst_ops, dev, - 0, 0, flags); + 0, DST_OBSOLETE_NONE, flags); if (rt) { struct dst_entry *dst = &rt->dst; @@ -985,7 +985,7 @@ struct dst_entry *ip6_blackhole_route(struct net *net, struct dst_entry *dst_ori struct rt6_info *rt, *ort = (struct rt6_info *) dst_orig; struct dst_entry *new = NULL; - rt = dst_alloc(&ip6_dst_blackhole_ops, ort->dst.dev, 1, 0, 0); + rt = dst_alloc(&ip6_dst_blackhole_ops, ort->dst.dev, 1, DST_OBSOLETE_NONE, 0); if (rt) { new = &rt->dst; diff --git a/net/sctp/transport.c b/net/sctp/transport.c index a6b7ee9..ec3a12b 100644 --- a/net/sctp/transport.c +++ b/net/sctp/transport.c @@ -216,7 +216,7 @@ void sctp_transport_set_owner(struct sctp_transport *transport, void sctp_transport_pmtu(struct sctp_transport *transport, struct sock *sk) { /* If we don't have a fresh route, look one up */ - if (!transport->dst || transport->dst->obsolete > 1) { + if (!transport->dst || transport->dst->obsolete) { dst_release(transport->dst); transport->af_specific->get_dst(transport, &transport->saddr, &transport->fl, sk); diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c index 65bd1ca5..c5a5165 100644 --- a/net/xfrm/xfrm_policy.c +++ b/net/xfrm/xfrm_policy.c @@ -1350,7 +1350,7 @@ static inline struct xfrm_dst *xfrm_alloc_dst(struct net *net, int family) default: BUG(); } - xdst = dst_alloc(dst_ops, NULL, 0, 0, 0); + xdst = dst_alloc(dst_ops, NULL, 0, DST_OBSOLETE_NONE, 0); if (likely(xdst)) { struct dst_entry *dst = &xdst->u.dst; @@ -1477,7 +1477,7 @@ static struct dst_entry *xfrm_bundle_create(struct xfrm_policy *policy, dst1->xfrm = xfrm[i]; xdst->xfrm_genid = xfrm[i]->genid; - dst1->obsolete = -1; + dst1->obsolete = DST_OBSOLETE_FORCE_CHK; dst1->flags |= DST_HOST; dst1->lastuse = now; @@ -2219,12 +2219,13 @@ EXPORT_SYMBOL(__xfrm_route_forward); static struct dst_entry *xfrm_dst_check(struct dst_entry *dst, u32 cookie) { /* Code (such as __xfrm4_bundle_create()) sets dst->obsolete - * to "-1" to force all XFRM destinations to get validated by - * dst_ops->check on every use. We do this because when a - * normal route referenced by an XFRM dst is obsoleted we do - * not go looking around for all parent referencing XFRM dsts - * so that we can invalidate them. It is just too much work. - * Instead we make the checks here on every use. For example: + * to DST_OBSOLETE_FORCE_CHK to force all XFRM destinations to + * get validated by dst_ops->check on every use. We do this + * because when a normal route referenced by an XFRM dst is + * obsoleted we do not go looking around for all parent + * referencing XFRM dsts so that we can invalidate them. It + * is just too much work. Instead we make the checks here on + * every use. For example: * * XFRM dst A --> IPv4 dst X * @@ -2234,9 +2235,9 @@ static struct dst_entry *xfrm_dst_check(struct dst_entry *dst, u32 cookie) * stale_bundle() check. * * When a policy's bundle is pruned, we dst_free() the XFRM - * dst which causes it's ->obsolete field to be set to a - * positive non-zero integer. If an XFRM dst has been pruned - * like this, we want to force a new route lookup. + * dst which causes it's ->obsolete field to be set to + * DST_OBSOLETE_DEAD. If an XFRM dst has been pruned like + * this, we want to force a new route lookup. */ if (dst->obsolete < 0 && !stale_bundle(dst)) return dst; -- cgit v0.10.2