From: dsahern@kernel•org
To: netdev@vger•kernel.org, borkmann@iogearbox•net, ast@kernel•org
Cc: davem@davemloft•net, David Ahern <dsahern@gmail•com>
Subject: [PATCH v2 bpf-next 3/3] bpf: Add mtu checking to FIB forwarding helper
Date: Mon, 21 May 2018 09:08:15 -0700 [thread overview]
Message-ID: <20180521160816.7060-4-dsahern@kernel.org> (raw)
In-Reply-To: <20180521160816.7060-1-dsahern@kernel.org>
From: David Ahern <dsahern@gmail•com>
Add check that egress MTU can handle packet to be forwarded. If
the MTU is less than the packet length, return 0 meaning the
packet is expected to continue up the stack for help - eg.,
fragmenting the packet or sending an ICMP.
The XDP path needs to leverage the FIB entry for an MTU on the
route spec or an exception entry for a given destination. The
skb path lets is_skb_forwardable decide if the packet can be
sent.
Signed-off-by: David Ahern <dsahern@gmail•com>
---
net/core/filter.c | 42 +++++++++++++++++++++++++++++++++++-------
1 file changed, 35 insertions(+), 7 deletions(-)
diff --git a/net/core/filter.c b/net/core/filter.c
index aec5ebafb262..ba3ff5aa575a 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4089,7 +4089,7 @@ static int bpf_fib_set_fwd_params(struct bpf_fib_lookup *params,
#if IS_ENABLED(CONFIG_INET)
static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
- u32 flags)
+ u32 flags, bool check_mtu)
{
struct in_device *in_dev;
struct neighbour *neigh;
@@ -4098,6 +4098,7 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
struct fib_nh *nh;
struct flowi4 fl4;
int err;
+ u32 mtu;
dev = dev_get_by_index_rcu(net, params->ifindex);
if (unlikely(!dev))
@@ -4149,6 +4150,12 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
if (res.fi->fib_nhs > 1)
fib_select_path(net, &res, &fl4, NULL);
+ if (check_mtu) {
+ mtu = ip_mtu_from_fib_result(&res, params->ipv4_dst);
+ if (params->tot_len > mtu)
+ return 0;
+ }
+
nh = &res.fi->fib_nh[res.nh_sel];
/* do not handle lwt encaps right now */
@@ -4177,7 +4184,7 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
#if IS_ENABLED(CONFIG_IPV6)
static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
- u32 flags)
+ u32 flags, bool check_mtu)
{
struct in6_addr *src = (struct in6_addr *) params->ipv6_src;
struct in6_addr *dst = (struct in6_addr *) params->ipv6_dst;
@@ -4188,6 +4195,7 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
struct flowi6 fl6;
int strict = 0;
int oif;
+ u32 mtu;
/* link local addresses are never forwarded */
if (rt6_need_strict(dst) || rt6_need_strict(src))
@@ -4250,6 +4258,12 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
fl6.flowi6_oif, NULL,
strict);
+ if (check_mtu) {
+ mtu = ipv6_stub->ip6_mtu_from_fib6(f6i, dst, src);
+ if (params->tot_len > mtu)
+ return 0;
+ }
+
if (f6i->fib6_nh.nh_lwtstate)
return 0;
@@ -4282,12 +4296,12 @@ BPF_CALL_4(bpf_xdp_fib_lookup, struct xdp_buff *, ctx,
#if IS_ENABLED(CONFIG_INET)
case AF_INET:
return bpf_ipv4_fib_lookup(dev_net(ctx->rxq->dev), params,
- flags);
+ flags, true);
#endif
#if IS_ENABLED(CONFIG_IPV6)
case AF_INET6:
return bpf_ipv6_fib_lookup(dev_net(ctx->rxq->dev), params,
- flags);
+ flags, true);
#endif
}
return 0;
@@ -4306,20 +4320,34 @@ static const struct bpf_func_proto bpf_xdp_fib_lookup_proto = {
BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb,
struct bpf_fib_lookup *, params, int, plen, u32, flags)
{
+ struct net *net = dev_net(skb->dev);
+ int index = 0;
+
if (plen < sizeof(*params))
return -EINVAL;
switch (params->family) {
#if IS_ENABLED(CONFIG_INET)
case AF_INET:
- return bpf_ipv4_fib_lookup(dev_net(skb->dev), params, flags);
+ index = bpf_ipv4_fib_lookup(net, params, flags, false);
+ break;
#endif
#if IS_ENABLED(CONFIG_IPV6)
case AF_INET6:
- return bpf_ipv6_fib_lookup(dev_net(skb->dev), params, flags);
+ index = bpf_ipv6_fib_lookup(net, params, flags, false);
+ break;
#endif
}
- return -ENOTSUPP;
+
+ if (index > 0) {
+ struct net_device *dev;
+
+ dev = dev_get_by_index_rcu(net, index);
+ if (!is_skb_forwardable(dev, skb))
+ index = 0;
+ }
+
+ return index;
}
static const struct bpf_func_proto bpf_skb_fib_lookup_proto = {
--
2.11.0
next prev parent reply other threads:[~2018-05-21 16:08 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-21 16:08 [PATCH v2 bpf-next 0/3] bpf: Add MTU check to fib lookup helper dsahern
2018-05-21 16:08 ` [PATCH v2 bpf-next 1/3] net/ipv4: Add helper to return path MTU based on fib result dsahern
2018-05-21 16:08 ` [PATCH v2 bpf-next 2/3] net/ipv6: " dsahern
2018-05-21 16:08 ` dsahern [this message]
2018-05-22 8:59 ` [PATCH v2 bpf-next 0/3] bpf: Add MTU check to fib lookup helper Daniel Borkmann
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