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af7888ad9e
FIB lookups can return an entry that references an external nexthop.
While walking the nexthop struct we do not want to make multiple calls
into the nexthop code which can result in 2 different structs getting
accessed - one returning the number of paths the rest of the loop
seeing a different nh_grp struct. If the nexthop group shrunk, the
result is an attempt to access a fib_nh_common that does not exist for
the new nh_grp struct but did for the old one.
To fix that move the device evaluation code to a helper that can be
used for inline fib_nh path as well as external nexthops.
Update the existing check for fi->nh in fib_table_lookup to call a
new helper, nexthop_get_nhc_lookup, which walks the external nexthop
with a single rcu dereference.
Fixes: 430a049190
("nexthop: Add support for nexthop groups")
Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
351 lines
7.2 KiB
C
351 lines
7.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Generic nexthop implementation
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*
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* Copyright (c) 2017-19 Cumulus Networks
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* Copyright (c) 2017-19 David Ahern <dsa@cumulusnetworks.com>
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*/
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#ifndef __LINUX_NEXTHOP_H
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#define __LINUX_NEXTHOP_H
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#include <linux/netdevice.h>
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#include <linux/route.h>
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#include <linux/types.h>
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#include <net/ip_fib.h>
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#include <net/ip6_fib.h>
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#include <net/netlink.h>
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#define NEXTHOP_VALID_USER_FLAGS RTNH_F_ONLINK
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struct nexthop;
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struct nh_config {
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u32 nh_id;
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u8 nh_family;
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u8 nh_protocol;
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u8 nh_blackhole;
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u32 nh_flags;
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int nh_ifindex;
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struct net_device *dev;
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union {
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__be32 ipv4;
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struct in6_addr ipv6;
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} gw;
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struct nlattr *nh_grp;
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u16 nh_grp_type;
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struct nlattr *nh_encap;
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u16 nh_encap_type;
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u32 nlflags;
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struct nl_info nlinfo;
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};
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struct nh_info {
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struct hlist_node dev_hash; /* entry on netns devhash */
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struct nexthop *nh_parent;
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u8 family;
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bool reject_nh;
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union {
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struct fib_nh_common fib_nhc;
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struct fib_nh fib_nh;
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struct fib6_nh fib6_nh;
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};
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};
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struct nh_grp_entry {
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struct nexthop *nh;
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u8 weight;
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atomic_t upper_bound;
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struct list_head nh_list;
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struct nexthop *nh_parent; /* nexthop of group with this entry */
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};
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struct nh_group {
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struct nh_group *spare; /* spare group for removals */
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u16 num_nh;
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bool mpath;
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bool has_v4;
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struct nh_grp_entry nh_entries[];
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};
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struct nexthop {
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struct rb_node rb_node; /* entry on netns rbtree */
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struct list_head fi_list; /* v4 entries using nh */
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struct list_head f6i_list; /* v6 entries using nh */
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struct list_head grp_list; /* nh group entries using this nh */
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struct net *net;
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u32 id;
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u8 protocol; /* app managing this nh */
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u8 nh_flags;
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bool is_group;
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refcount_t refcnt;
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struct rcu_head rcu;
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union {
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struct nh_info __rcu *nh_info;
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struct nh_group __rcu *nh_grp;
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};
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};
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/* caller is holding rcu or rtnl; no reference taken to nexthop */
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struct nexthop *nexthop_find_by_id(struct net *net, u32 id);
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void nexthop_free_rcu(struct rcu_head *head);
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static inline bool nexthop_get(struct nexthop *nh)
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{
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return refcount_inc_not_zero(&nh->refcnt);
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}
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static inline void nexthop_put(struct nexthop *nh)
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{
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if (refcount_dec_and_test(&nh->refcnt))
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call_rcu(&nh->rcu, nexthop_free_rcu);
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}
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static inline bool nexthop_cmp(const struct nexthop *nh1,
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const struct nexthop *nh2)
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{
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return nh1 == nh2;
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}
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static inline bool nexthop_is_multipath(const struct nexthop *nh)
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{
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if (nh->is_group) {
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struct nh_group *nh_grp;
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nh_grp = rcu_dereference_rtnl(nh->nh_grp);
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return nh_grp->mpath;
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}
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return false;
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}
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struct nexthop *nexthop_select_path(struct nexthop *nh, int hash);
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static inline unsigned int nexthop_num_path(const struct nexthop *nh)
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{
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unsigned int rc = 1;
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if (nh->is_group) {
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struct nh_group *nh_grp;
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nh_grp = rcu_dereference_rtnl(nh->nh_grp);
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if (nh_grp->mpath)
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rc = nh_grp->num_nh;
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}
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return rc;
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}
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static inline
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struct nexthop *nexthop_mpath_select(const struct nh_group *nhg, int nhsel)
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{
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/* for_nexthops macros in fib_semantics.c grabs a pointer to
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* the nexthop before checking nhsel
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*/
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if (nhsel >= nhg->num_nh)
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return NULL;
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return nhg->nh_entries[nhsel].nh;
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}
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static inline
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int nexthop_mpath_fill_node(struct sk_buff *skb, struct nexthop *nh,
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u8 rt_family)
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{
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struct nh_group *nhg = rtnl_dereference(nh->nh_grp);
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int i;
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for (i = 0; i < nhg->num_nh; i++) {
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struct nexthop *nhe = nhg->nh_entries[i].nh;
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struct nh_info *nhi = rcu_dereference_rtnl(nhe->nh_info);
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struct fib_nh_common *nhc = &nhi->fib_nhc;
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int weight = nhg->nh_entries[i].weight;
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if (fib_add_nexthop(skb, nhc, weight, rt_family) < 0)
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return -EMSGSIZE;
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}
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return 0;
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}
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/* called with rcu lock */
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static inline bool nexthop_is_blackhole(const struct nexthop *nh)
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{
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const struct nh_info *nhi;
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if (nh->is_group) {
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struct nh_group *nh_grp;
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nh_grp = rcu_dereference_rtnl(nh->nh_grp);
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if (nh_grp->num_nh > 1)
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return false;
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nh = nh_grp->nh_entries[0].nh;
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}
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nhi = rcu_dereference_rtnl(nh->nh_info);
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return nhi->reject_nh;
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}
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static inline void nexthop_path_fib_result(struct fib_result *res, int hash)
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{
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struct nh_info *nhi;
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struct nexthop *nh;
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nh = nexthop_select_path(res->fi->nh, hash);
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nhi = rcu_dereference(nh->nh_info);
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res->nhc = &nhi->fib_nhc;
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}
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/* called with rcu read lock or rtnl held */
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static inline
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struct fib_nh_common *nexthop_fib_nhc(struct nexthop *nh, int nhsel)
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{
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struct nh_info *nhi;
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BUILD_BUG_ON(offsetof(struct fib_nh, nh_common) != 0);
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BUILD_BUG_ON(offsetof(struct fib6_nh, nh_common) != 0);
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if (nh->is_group) {
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struct nh_group *nh_grp;
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nh_grp = rcu_dereference_rtnl(nh->nh_grp);
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if (nh_grp->mpath) {
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nh = nexthop_mpath_select(nh_grp, nhsel);
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if (!nh)
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return NULL;
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}
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}
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nhi = rcu_dereference_rtnl(nh->nh_info);
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return &nhi->fib_nhc;
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}
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/* called from fib_table_lookup with rcu_lock */
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static inline
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struct fib_nh_common *nexthop_get_nhc_lookup(const struct nexthop *nh,
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int fib_flags,
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const struct flowi4 *flp,
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int *nhsel)
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{
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struct nh_info *nhi;
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if (nh->is_group) {
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struct nh_group *nhg = rcu_dereference(nh->nh_grp);
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int i;
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for (i = 0; i < nhg->num_nh; i++) {
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struct nexthop *nhe = nhg->nh_entries[i].nh;
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nhi = rcu_dereference(nhe->nh_info);
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if (fib_lookup_good_nhc(&nhi->fib_nhc, fib_flags, flp)) {
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*nhsel = i;
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return &nhi->fib_nhc;
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}
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}
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} else {
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nhi = rcu_dereference(nh->nh_info);
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if (fib_lookup_good_nhc(&nhi->fib_nhc, fib_flags, flp)) {
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*nhsel = 0;
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return &nhi->fib_nhc;
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}
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}
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return NULL;
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}
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static inline unsigned int fib_info_num_path(const struct fib_info *fi)
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{
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if (unlikely(fi->nh))
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return nexthop_num_path(fi->nh);
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return fi->fib_nhs;
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}
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int fib_check_nexthop(struct nexthop *nh, u8 scope,
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struct netlink_ext_ack *extack);
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static inline struct fib_nh_common *fib_info_nhc(struct fib_info *fi, int nhsel)
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{
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if (unlikely(fi->nh))
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return nexthop_fib_nhc(fi->nh, nhsel);
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return &fi->fib_nh[nhsel].nh_common;
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}
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/* only used when fib_nh is built into fib_info */
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static inline struct fib_nh *fib_info_nh(struct fib_info *fi, int nhsel)
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{
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WARN_ON(fi->nh);
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return &fi->fib_nh[nhsel];
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}
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/*
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* IPv6 variants
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*/
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int fib6_check_nexthop(struct nexthop *nh, struct fib6_config *cfg,
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struct netlink_ext_ack *extack);
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static inline struct fib6_nh *nexthop_fib6_nh(struct nexthop *nh)
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{
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struct nh_info *nhi;
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if (nh->is_group) {
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struct nh_group *nh_grp;
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nh_grp = rcu_dereference_rtnl(nh->nh_grp);
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nh = nexthop_mpath_select(nh_grp, 0);
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if (!nh)
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return NULL;
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}
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nhi = rcu_dereference_rtnl(nh->nh_info);
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if (nhi->family == AF_INET6)
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return &nhi->fib6_nh;
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return NULL;
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}
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static inline struct net_device *fib6_info_nh_dev(struct fib6_info *f6i)
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{
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struct fib6_nh *fib6_nh;
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fib6_nh = f6i->nh ? nexthop_fib6_nh(f6i->nh) : f6i->fib6_nh;
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return fib6_nh->fib_nh_dev;
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}
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static inline void nexthop_path_fib6_result(struct fib6_result *res, int hash)
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{
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struct nexthop *nh = res->f6i->nh;
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struct nh_info *nhi;
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nh = nexthop_select_path(nh, hash);
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nhi = rcu_dereference_rtnl(nh->nh_info);
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if (nhi->reject_nh) {
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res->fib6_type = RTN_BLACKHOLE;
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res->fib6_flags |= RTF_REJECT;
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res->nh = nexthop_fib6_nh(nh);
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} else {
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res->nh = &nhi->fib6_nh;
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}
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}
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int nexthop_for_each_fib6_nh(struct nexthop *nh,
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int (*cb)(struct fib6_nh *nh, void *arg),
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void *arg);
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#endif
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