Add ipip6 and ip6ip decap support for bpf_skb_adjust_room().
Main use case is for using cls_bpf on ingress hook to decapsulate
IPv4 over IPv6 and IPv6 over IPv4 tunnel packets.
Add two new flags BPF_F_ADJ_ROOM_DECAP_L3_IPV{4,6} to indicate the
new IP header version after decapsulating the outer IP header.
Suggested-by: Willem de Bruijn <willemb@xxxxxxxxxx>
Signed-off-by: Ziyang Xuan <william.xuanziyang@xxxxxxxxxx>
---
include/uapi/linux/bpf.h | 8 ++++++++
net/core/filter.c | 26 +++++++++++++++++++++++++-
tools/include/uapi/linux/bpf.h | 8 ++++++++
3 files changed, 41 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 464ca3f01fe7..dde1c2ea1c84 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2644,6 +2644,12 @@ union bpf_attr {
* Use with BPF_F_ADJ_ROOM_ENCAP_L2 flag to further specify the
* L2 type as Ethernet.
*
+ * * **BPF_F_ADJ_ROOM_DECAP_L3_IPV4**,
+ * **BPF_F_ADJ_ROOM_DECAP_L3_IPV6**:
+ * Indicate the new IP header version after decapsulating the
+ * outer IP header. Mainly used in scenarios that the inner and
+ * outer IP versions are different.
+ *
* A call to this helper is susceptible to change the underlying
* packet buffer. Therefore, at load time, all checks on pointers
* previously done by the verifier are invalidated and must be
@@ -5803,6 +5809,8 @@ enum {
BPF_F_ADJ_ROOM_ENCAP_L4_UDP = (1ULL << 4),
BPF_F_ADJ_ROOM_NO_CSUM_RESET = (1ULL << 5),
BPF_F_ADJ_ROOM_ENCAP_L2_ETH = (1ULL << 6),
+ BPF_F_ADJ_ROOM_DECAP_L3_IPV4 = (1ULL << 7),
+ BPF_F_ADJ_ROOM_DECAP_L3_IPV6 = (1ULL << 8),
};
enum {
diff --git a/net/core/filter.c b/net/core/filter.c
index 43cc1fe58a2c..5fb113953f80 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3381,13 +3381,17 @@ static u32 bpf_skb_net_base_len(const struct sk_buff *skb)
#define BPF_F_ADJ_ROOM_ENCAP_L3_MASK (BPF_F_ADJ_ROOM_ENCAP_L3_IPV4 | \
BPF_F_ADJ_ROOM_ENCAP_L3_IPV6)
+#define BPF_F_ADJ_ROOM_DECAP_L3_MASK (BPF_F_ADJ_ROOM_DECAP_L3_IPV4 | \
+ BPF_F_ADJ_ROOM_DECAP_L3_IPV6)
+
#define BPF_F_ADJ_ROOM_MASK (BPF_F_ADJ_ROOM_FIXED_GSO | \
BPF_F_ADJ_ROOM_ENCAP_L3_MASK | \
BPF_F_ADJ_ROOM_ENCAP_L4_GRE | \
BPF_F_ADJ_ROOM_ENCAP_L4_UDP | \
BPF_F_ADJ_ROOM_ENCAP_L2_ETH | \
BPF_F_ADJ_ROOM_ENCAP_L2( \
- BPF_ADJ_ROOM_ENCAP_L2_MASK))
+ BPF_ADJ_ROOM_ENCAP_L2_MASK) | \
+ BPF_F_ADJ_ROOM_DECAP_L3_MASK)
static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, u32 len_diff,
u64 flags)
@@ -3501,6 +3505,7 @@ static int bpf_skb_net_shrink(struct sk_buff *skb, u32 off, u32 len_diff,
int ret;
if (unlikely(flags & ~(BPF_F_ADJ_ROOM_FIXED_GSO |
+ BPF_F_ADJ_ROOM_DECAP_L3_MASK |
BPF_F_ADJ_ROOM_NO_CSUM_RESET)))
return -EINVAL;
@@ -3519,6 +3524,14 @@ static int bpf_skb_net_shrink(struct sk_buff *skb, u32 off, u32 len_diff,
if (unlikely(ret < 0))
return ret;
+ /* Match skb->protocol to new outer l3 protocol */
+ if (skb->protocol == htons(ETH_P_IP) &&
+ flags & BPF_F_ADJ_ROOM_DECAP_L3_IPV6)
+ skb->protocol = htons(ETH_P_IPV6);
+ else if (skb->protocol == htons(ETH_P_IPV6) &&
+ flags & BPF_F_ADJ_ROOM_DECAP_L3_IPV4)
+ skb->protocol = htons(ETH_P_IP);
+
if (skb_is_gso(skb)) {
struct skb_shared_info *shinfo = skb_shinfo(skb);
@@ -3596,6 +3609,10 @@ BPF_CALL_4(bpf_skb_adjust_room, struct sk_buff *, skb, s32, len_diff,
if (unlikely(proto != htons(ETH_P_IP) &&
proto != htons(ETH_P_IPV6)))
return -ENOTSUPP;
+ if (unlikely((shrink && ((flags & BPF_F_ADJ_ROOM_DECAP_L3_MASK) ==
+ BPF_F_ADJ_ROOM_DECAP_L3_MASK)) || (!shrink &&
+ flags & BPF_F_ADJ_ROOM_DECAP_L3_MASK)))
+ return -EINVAL;
off = skb_mac_header_len(skb);
switch (mode) {
@@ -3608,6 +3625,13 @@ BPF_CALL_4(bpf_skb_adjust_room, struct sk_buff *, skb, s32, len_diff,
return -ENOTSUPP;
}
+ if (shrink) {
+ if (flags & BPF_F_ADJ_ROOM_DECAP_L3_IPV6)
+ len_min = sizeof(struct ipv6hdr);
+ else if (flags & BPF_F_ADJ_ROOM_DECAP_L3_IPV4)
+ len_min = sizeof(struct iphdr);
+ }
+
len_cur = skb->len - skb_network_offset(skb);
if ((shrink && (len_diff_abs >= len_cur ||
len_cur - len_diff_abs < len_min)) ||
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 464ca3f01fe7..22672e5c8466 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -2644,6 +2644,12 @@ union bpf_attr {
* Use with BPF_F_ADJ_ROOM_ENCAP_L2 flag to further specify the
* L2 type as Ethernet.
*
+ * * **BPF_F_ADJ_ROOM_DECAP_L3_IPV4**,
+ * **BPF_F_ADJ_ROOM_DECAP_L3_IPV6**:
+ * Indicate the new IP header version after decapsulating the
+ * outer IP header. Mainly used in scenarios that the inner and
+ * outer IP versions are different.
+ *
* A call to this helper is susceptible to change the underlying
* packet buffer. Therefore, at load time, all checks on pointers
* previously done by the verifier are invalidated and must be
@@ -5803,6 +5809,8 @@ enum {
BPF_F_ADJ_ROOM_ENCAP_L4_UDP = (1ULL << 4),
BPF_F_ADJ_ROOM_NO_CSUM_RESET = (1ULL << 5),
BPF_F_ADJ_ROOM_ENCAP_L2_ETH = (1ULL << 6),
+ BPF_F_ADJ_ROOM_DECAP_L3_IPV4 = (1ULL << 7),
+ BPF_F_ADJ_ROOM_DECAP_L3_IPV6 = (1ULL << 8),
};
enum {
--
2.25.1
