From: Jesper Dangaard Brouer <brouer@redhat.com>
To: bpf@vger.kernel.org
Cc: Jesper Dangaard Brouer <brouer@redhat.com>,
netdev@vger.kernel.org, Daniel Borkmann <borkmann@iogearbox.net>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
maze@google.com, lmb@cloudflare.com, shaun@tigera.io,
Lorenzo Bianconi <lorenzo@kernel.org>,
marek@cloudflare.com, John Fastabend <john.fastabend@gmail.com>,
Jakub Kicinski <kuba@kernel.org>,
eyal.birger@gmail.com, colrack@gmail.com
Subject: [PATCH bpf-next V11 5/7] bpf: drop MTU check when doing TC-BPF redirect to ingress
Date: Tue, 12 Jan 2021 18:45:25 +0100 [thread overview]
Message-ID: <161047352593.4003084.6778762780747210369.stgit@firesoul> (raw)
In-Reply-To: <161047346644.4003084.2653117664787086168.stgit@firesoul>
The use-case for dropping the MTU check when TC-BPF does redirect to
ingress, is described by Eyal Birger in email[0]. The summary is the
ability to increase packet size (e.g. with IPv6 headers for NAT64) and
ingress redirect packet and let normal netstack fragment packet as needed.
[0] https://lore.kernel.org/netdev/CAHsH6Gug-hsLGHQ6N0wtixdOa85LDZ3HNRHVd0opR=19Qo4W4Q@mail.gmail.com/
V9:
- Make net_device "up" (IFF_UP) check explicit in skb_do_redirect
V4:
- Keep net_device "up" (IFF_UP) check.
- Adjustment to handle bpf_redirect_peer() helper
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
include/linux/netdevice.h | 31 +++++++++++++++++++++++++++++--
net/core/dev.c | 19 ++-----------------
net/core/filter.c | 14 +++++++++++---
3 files changed, 42 insertions(+), 22 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 1ec3ac5d5bbf..438943f98a9c 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3930,11 +3930,38 @@ int dev_forward_skb(struct net_device *dev, struct sk_buff *skb);
bool is_skb_forwardable(const struct net_device *dev,
const struct sk_buff *skb);
+static __always_inline bool __is_skb_forwardable(const struct net_device *dev,
+ const struct sk_buff *skb,
+ const bool check_mtu)
+{
+ const u32 vlan_hdr_len = 4; /* VLAN_HLEN */
+ unsigned int len;
+
+ if (!(dev->flags & IFF_UP))
+ return false;
+
+ if (!check_mtu)
+ return true;
+
+ len = dev->mtu + dev->hard_header_len + vlan_hdr_len;
+ if (skb->len <= len)
+ return true;
+
+ /* if TSO is enabled, we don't care about the length as the packet
+ * could be forwarded without being segmented before
+ */
+ if (skb_is_gso(skb))
+ return true;
+
+ return false;
+}
+
static __always_inline int ____dev_forward_skb(struct net_device *dev,
- struct sk_buff *skb)
+ struct sk_buff *skb,
+ const bool check_mtu)
{
if (skb_orphan_frags(skb, GFP_ATOMIC) ||
- unlikely(!is_skb_forwardable(dev, skb))) {
+ unlikely(!__is_skb_forwardable(dev, skb, check_mtu))) {
atomic_long_inc(&dev->rx_dropped);
kfree_skb(skb);
return NET_RX_DROP;
diff --git a/net/core/dev.c b/net/core/dev.c
index 55499b017a42..51bc7f079958 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2194,28 +2194,13 @@ static inline void net_timestamp_set(struct sk_buff *skb)
bool is_skb_forwardable(const struct net_device *dev, const struct sk_buff *skb)
{
- unsigned int len;
-
- if (!(dev->flags & IFF_UP))
- return false;
-
- len = dev->mtu + dev->hard_header_len + VLAN_HLEN;
- if (skb->len <= len)
- return true;
-
- /* if TSO is enabled, we don't care about the length as the packet
- * could be forwarded without being segmented before
- */
- if (skb_is_gso(skb))
- return true;
-
- return false;
+ return __is_skb_forwardable(dev, skb, true);
}
EXPORT_SYMBOL_GPL(is_skb_forwardable);
int __dev_forward_skb(struct net_device *dev, struct sk_buff *skb)
{
- int ret = ____dev_forward_skb(dev, skb);
+ int ret = ____dev_forward_skb(dev, skb, true);
if (likely(!ret)) {
skb->protocol = eth_type_trans(skb, dev);
diff --git a/net/core/filter.c b/net/core/filter.c
index 3f2e593244ca..1908800b671c 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2083,13 +2083,21 @@ static const struct bpf_func_proto bpf_csum_level_proto = {
static inline int __bpf_rx_skb(struct net_device *dev, struct sk_buff *skb)
{
- return dev_forward_skb(dev, skb);
+ int ret = ____dev_forward_skb(dev, skb, false);
+
+ if (likely(!ret)) {
+ skb->protocol = eth_type_trans(skb, dev);
+ skb_postpull_rcsum(skb, eth_hdr(skb), ETH_HLEN);
+ ret = netif_rx(skb);
+ }
+
+ return ret;
}
static inline int __bpf_rx_skb_no_mac(struct net_device *dev,
struct sk_buff *skb)
{
- int ret = ____dev_forward_skb(dev, skb);
+ int ret = ____dev_forward_skb(dev, skb, false);
if (likely(!ret)) {
skb->dev = dev;
@@ -2480,7 +2488,7 @@ int skb_do_redirect(struct sk_buff *skb)
goto out_drop;
dev = ops->ndo_get_peer_dev(dev);
if (unlikely(!dev ||
- !is_skb_forwardable(dev, skb) ||
+ !(dev->flags & IFF_UP) ||
net_eq(net, dev_net(dev))))
goto out_drop;
skb->dev = dev;
next prev parent reply other threads:[~2021-01-12 17:47 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-12 17:45 [PATCH bpf-next V11 0/7] bpf: New approach for BPF MTU handling Jesper Dangaard Brouer
2021-01-12 17:45 ` [PATCH bpf-next V11 1/7] bpf: Remove MTU check in __bpf_skb_max_len Jesper Dangaard Brouer
2021-01-14 8:18 ` John Fastabend
2021-01-12 17:45 ` [PATCH bpf-next V11 2/7] bpf: fix bpf_fib_lookup helper MTU check for SKB ctx Jesper Dangaard Brouer
2021-01-12 17:45 ` [PATCH bpf-next V11 3/7] bpf: bpf_fib_lookup return MTU value as output when looked up Jesper Dangaard Brouer
2021-01-12 17:45 ` [PATCH bpf-next V11 4/7] bpf: add BPF-helper for MTU checking Jesper Dangaard Brouer
2021-01-12 19:23 ` Andrii Nakryiko
2021-01-14 14:52 ` Jesper Dangaard Brouer
2021-01-14 15:33 ` Yonghong Song
2021-01-13 23:07 ` Daniel Borkmann
2021-01-14 14:36 ` Jesper Dangaard Brouer
2021-01-14 22:28 ` Daniel Borkmann
2021-01-18 11:04 ` Jesper Dangaard Brouer
2021-01-12 17:45 ` Jesper Dangaard Brouer [this message]
2021-01-14 9:03 ` [PATCH bpf-next V11 5/7] bpf: drop MTU check when doing TC-BPF redirect to ingress John Fastabend
2021-01-14 16:14 ` Jesper Dangaard Brouer
2021-01-12 17:45 ` [PATCH bpf-next V11 6/7] selftests/bpf: use bpf_check_mtu in selftest test_cls_redirect Jesper Dangaard Brouer
2021-01-12 17:45 ` [PATCH bpf-next V11 7/7] bpf/selftests: tests using bpf_check_mtu BPF-helper Jesper Dangaard Brouer
2021-01-12 19:29 ` Andrii Nakryiko
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