@@ -3947,11 +3947,38 @@ 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;
@@ -2176,28 +2176,13 @@ 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);
@@ -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;
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(-)