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Message-ID: <161217675170.494501.11194096254681150724.stgit@firesoul>
Date: Mon, 01 Feb 2021 11:52:31 +0100
From: Jesper Dangaard Brouer <brouer@...hat.com>
To: bpf@...r.kernel.org
Cc: Jesper Dangaard Brouer <brouer@...hat.com>, netdev@...r.kernel.org,
Daniel Borkmann <borkmann@...earbox.net>,
Alexei Starovoitov <alexei.starovoitov@...il.com>,
maze@...gle.com, lmb@...udflare.com, shaun@...era.io,
Lorenzo Bianconi <lorenzo@...nel.org>, marek@...udflare.com,
John Fastabend <john.fastabend@...il.com>,
Jakub Kicinski <kuba@...nel.org>, eyal.birger@...il.com,
colrack@...il.com
Subject: [PATCH bpf-next V14 5/7] bpf: drop MTU check when doing TC-BPF
redirect to ingress
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@...hat.com>
Acked-by: John Fastabend <john.fastabend@...il.com>
---
include/linux/netdevice.h | 32 ++++++++++++++++++++++++++++++--
net/core/dev.c | 32 ++++++++++++++------------------
net/core/filter.c | 6 +++---
3 files changed, 47 insertions(+), 23 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 5b949076ed23..b7915484369c 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3926,14 +3926,42 @@ int xdp_umem_query(struct net_device *dev, u16 queue_id);
int __dev_forward_skb(struct net_device *dev, struct sk_buff *skb);
int dev_forward_skb(struct net_device *dev, struct sk_buff *skb);
+int dev_forward_skb_nomtu(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 bae35c1ae192..87bb2cd62189 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2194,28 +2194,14 @@ 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 __dev_forward_skb2(struct net_device *dev, struct sk_buff *skb,
+ bool check_mtu)
{
- int ret = ____dev_forward_skb(dev, skb);
+ int ret = ____dev_forward_skb(dev, skb, check_mtu);
if (likely(!ret)) {
skb->protocol = eth_type_trans(skb, dev);
@@ -2224,6 +2210,11 @@ int __dev_forward_skb(struct net_device *dev, struct sk_buff *skb)
return ret;
}
+
+int __dev_forward_skb(struct net_device *dev, struct sk_buff *skb)
+{
+ return __dev_forward_skb2(dev, skb, true);
+}
EXPORT_SYMBOL_GPL(__dev_forward_skb);
/**
@@ -2250,6 +2241,11 @@ int dev_forward_skb(struct net_device *dev, struct sk_buff *skb)
}
EXPORT_SYMBOL_GPL(dev_forward_skb);
+int dev_forward_skb_nomtu(struct net_device *dev, struct sk_buff *skb)
+{
+ return __dev_forward_skb2(dev, skb, false) ?: netif_rx_internal(skb);
+}
+
static inline int deliver_skb(struct sk_buff *skb,
struct packet_type *pt_prev,
struct net_device *orig_dev)
diff --git a/net/core/filter.c b/net/core/filter.c
index f6777e8f9ff7..28735dbb7059 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2083,13 +2083,13 @@ 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);
+ return dev_forward_skb_nomtu(dev, skb);
}
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 +2480,7 @@ 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;
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