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[bpf-next,V2,6/6] bpf: drop MTU check when doing TC-BPF redirect to ingress

Message ID 160208778579.798237.7257307543620328206.stgit@firesoul
State Superseded
Headers show
Series bpf: New approach for BPF MTU handling and enforcement | expand

Commit Message

Jesper Dangaard Brouer Oct. 7, 2020, 4:23 p.m. UTC 
The use-case for dropping the MTU check when TC-BPF ingress redirecting a
packet, 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/

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 include/linux/netdevice.h |    5 +++--
 net/core/dev.c            |    2 +-
 net/core/filter.c         |   12 ++++++++++--
 3 files changed, 14 insertions(+), 5 deletions(-)
diff mbox series

Patch

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 28cfa53daf72..58fb7b4869ba 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3866,10 +3866,11 @@  bool is_skb_forwardable(const struct net_device *dev,
 			const struct sk_buff *skb);
 
 static __always_inline int ____dev_forward_skb(struct net_device *dev,
-					       struct sk_buff *skb)
+					       struct sk_buff *skb,
+					       const bool mtu_check)
 {
 	if (skb_orphan_frags(skb, GFP_ATOMIC) ||
-	    unlikely(!is_skb_forwardable(dev, skb))) {
+	    (mtu_check && unlikely(!is_skb_forwardable(dev, skb)))) {
 		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 19406013f93e..bae95ae9aa96 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2209,7 +2209,7 @@  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 54b779e34f83..5516d4efe225 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;