diff options
author | Guillaume Nault <gnault@redhat.com> | 2022-03-17 15:45:09 +0300 |
---|---|---|
committer | Jakub Kicinski <kuba@kernel.org> | 2022-03-19 00:06:45 +0300 |
commit | 544b4dd568e3b09c1ab38a759d3187e7abda11a0 (patch) | |
tree | 2537d6ff122d9842f4f467db07ebb4451bb9fc1b /net/ipv4/route.c | |
parent | 6bd0c76bd70447aedfeafa9e1fcc249991d6c678 (diff) | |
download | linux-544b4dd568e3b09c1ab38a759d3187e7abda11a0.tar.xz |
ipv4: Fix route lookups when handling ICMP redirects and PMTU updates
The PMTU update and ICMP redirect helper functions initialise their fl4
variable with either __build_flow_key() or build_sk_flow_key(). These
initialisation functions always set ->flowi4_scope with
RT_SCOPE_UNIVERSE and might set the ECN bits of ->flowi4_tos. This is
not a problem when the route lookup is later done via
ip_route_output_key_hash(), which properly clears the ECN bits from
->flowi4_tos and initialises ->flowi4_scope based on the RTO_ONLINK
flag. However, some helpers call fib_lookup() directly, without
sanitising the tos and scope fields, so the route lookup can fail and,
as a result, the ICMP redirect or PMTU update aren't taken into
account.
Fix this by extracting the ->flowi4_tos and ->flowi4_scope sanitisation
code into ip_rt_fix_tos(), then use this function in handlers that call
fib_lookup() directly.
Note 1: We can't sanitise ->flowi4_tos and ->flowi4_scope in a central
place (like __build_flow_key() or flowi4_init_output()), because
ip_route_output_key_hash() expects non-sanitised values. When called
with sanitised values, it can erroneously overwrite RT_SCOPE_LINK with
RT_SCOPE_UNIVERSE in ->flowi4_scope. Therefore we have to be careful to
sanitise the values only for those paths that don't call
ip_route_output_key_hash().
Note 2: The problem is mostly about sanitising ->flowi4_tos. Having
->flowi4_scope initialised with RT_SCOPE_UNIVERSE instead of
RT_SCOPE_LINK probably wasn't really a problem: sockets with the
SOCK_LOCALROUTE flag set (those that'd result in RTO_ONLINK being set)
normally shouldn't receive ICMP redirects or PMTU updates.
Fixes: 4895c771c7f0 ("ipv4: Add FIB nexthop exceptions.")
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/ipv4/route.c')
-rw-r--r-- | net/ipv4/route.c | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/net/ipv4/route.c b/net/ipv4/route.c index f33ad1f383b6..d5d058de3664 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -499,6 +499,15 @@ void __ip_select_ident(struct net *net, struct iphdr *iph, int segs) } EXPORT_SYMBOL(__ip_select_ident); +static void ip_rt_fix_tos(struct flowi4 *fl4) +{ + __u8 tos = RT_FL_TOS(fl4); + + fl4->flowi4_tos = tos & IPTOS_RT_MASK; + fl4->flowi4_scope = tos & RTO_ONLINK ? + RT_SCOPE_LINK : RT_SCOPE_UNIVERSE; +} + static void __build_flow_key(const struct net *net, struct flowi4 *fl4, const struct sock *sk, const struct iphdr *iph, @@ -824,6 +833,7 @@ static void ip_do_redirect(struct dst_entry *dst, struct sock *sk, struct sk_buf rt = (struct rtable *) dst; __build_flow_key(net, &fl4, sk, iph, oif, tos, prot, mark, 0); + ip_rt_fix_tos(&fl4); __ip_do_redirect(rt, skb, &fl4, true); } @@ -1048,6 +1058,7 @@ static void ip_rt_update_pmtu(struct dst_entry *dst, struct sock *sk, struct flowi4 fl4; ip_rt_build_flow_key(&fl4, sk, skb); + ip_rt_fix_tos(&fl4); /* Don't make lookup fail for bridged encapsulations */ if (skb && netif_is_any_bridge_port(skb->dev)) @@ -1122,6 +1133,8 @@ void ipv4_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, u32 mtu) goto out; new = true; + } else { + ip_rt_fix_tos(&fl4); } __ip_rt_update_pmtu((struct rtable *)xfrm_dst_path(&rt->dst), &fl4, mtu); @@ -2603,7 +2616,6 @@ add: struct rtable *ip_route_output_key_hash(struct net *net, struct flowi4 *fl4, const struct sk_buff *skb) { - __u8 tos = RT_FL_TOS(fl4); struct fib_result res = { .type = RTN_UNSPEC, .fi = NULL, @@ -2613,9 +2625,7 @@ struct rtable *ip_route_output_key_hash(struct net *net, struct flowi4 *fl4, struct rtable *rth; fl4->flowi4_iif = LOOPBACK_IFINDEX; - fl4->flowi4_tos = tos & IPTOS_RT_MASK; - fl4->flowi4_scope = ((tos & RTO_ONLINK) ? - RT_SCOPE_LINK : RT_SCOPE_UNIVERSE); + ip_rt_fix_tos(fl4); rcu_read_lock(); rth = ip_route_output_key_hash_rcu(net, fl4, &res, skb); |