[PATCH v6 1/6] bpf: name the enum for BPF_FUNC_skb_adjust_room flags

[PATCH v6 1/6] bpf: name the enum for BPF_FUNC_skb_adjust_room flags

[Nick Hudson]

The existing anonymous enum for BPF_FUNC_skb_adjust_room flags is
named to enum bpf_adj_room_flags to enable CO-RE (Compile Once -
Run Everywhere) lookups in BPF programs.

Co-developed-by: Max Tottenham <mtottenh@akamai.com>
Signed-off-by: Max Tottenham <mtottenh@akamai.com>
Co-developed-by: Anna Glasgall <aglasgal@akamai.com>
Signed-off-by: Anna Glasgall <aglasgal@akamai.com>
Signed-off-by: Nick Hudson <nhudson@akamai.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
---
 include/uapi/linux/bpf.h       | 2 +-
 tools/include/uapi/linux/bpf.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 552bc5d9afbd..c021ed8d7b44 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -6211,7 +6211,7 @@ enum {
 };
 
 /* BPF_FUNC_skb_adjust_room flags. */
-enum {
+enum bpf_adj_room_flags {
 	BPF_F_ADJ_ROOM_FIXED_GSO	= (1ULL << 0),
 	BPF_F_ADJ_ROOM_ENCAP_L3_IPV4	= (1ULL << 1),
 	BPF_F_ADJ_ROOM_ENCAP_L3_IPV6	= (1ULL << 2),
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 677be9a47347..ca35ed622ed5 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -6211,7 +6211,7 @@ enum {
 };
 
 /* BPF_FUNC_skb_adjust_room flags. */
-enum {
+enum bpf_adj_room_flags {
 	BPF_F_ADJ_ROOM_FIXED_GSO	= (1ULL << 0),
 	BPF_F_ADJ_ROOM_ENCAP_L3_IPV4	= (1ULL << 1),
 	BPF_F_ADJ_ROOM_ENCAP_L3_IPV6	= (1ULL << 2),
-- 
2.34.1

[PATCH v6 2/6] bpf: refactor masks for ADJ_ROOM flags and encap validation

[Nick Hudson]

Refactor the helper masks for bpf_skb_adjust_room() flags to simplify
validation logic and introduce:

- BPF_F_ADJ_ROOM_ENCAP_MASK
- BPF_F_ADJ_ROOM_DECAP_MASK

Refactor existing validation checks in bpf_skb_net_shrink()
and bpf_skb_adjust_room() to use the new masks (no behavior change).

This is in preparation for supporting the new decap flags.

Co-developed-by: Max Tottenham <mtottenh@akamai.com>
Signed-off-by: Max Tottenham <mtottenh@akamai.com>
Co-developed-by: Anna Glasgall <aglasgal@akamai.com>
Signed-off-by: Anna Glasgall <aglasgal@akamai.com>
Signed-off-by: Nick Hudson <nhudson@akamai.com>
---
---
 net/core/filter.c | 38 +++++++++++++++++++++-----------------
 1 file changed, 21 insertions(+), 17 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 80a3b702a2d4..02d3947cca32 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3484,14 +3484,19 @@ static u32 bpf_skb_net_base_len(const struct sk_buff *skb)
 #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 | \
+#define BPF_F_ADJ_ROOM_ENCAP_MASK	(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_F_ADJ_ROOM_DECAP_L3_MASK)
+					  BPF_ADJ_ROOM_ENCAP_L2_MASK))
+
+#define BPF_F_ADJ_ROOM_DECAP_MASK	(BPF_F_ADJ_ROOM_DECAP_L3_MASK)
+
+#define BPF_F_ADJ_ROOM_MASK		(BPF_F_ADJ_ROOM_FIXED_GSO | \
+					 BPF_F_ADJ_ROOM_ENCAP_MASK | \
+					 BPF_F_ADJ_ROOM_DECAP_MASK | \
+					 BPF_F_ADJ_ROOM_NO_CSUM_RESET)
 
 static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, u32 len_diff,
 			    u64 flags)
@@ -3614,8 +3619,8 @@ static int bpf_skb_net_shrink(struct sk_buff *skb, u32 off, u32 len_diff,
 	bool decap = flags & BPF_F_ADJ_ROOM_DECAP_L3_MASK;
 	int ret;
 
-	if (unlikely(flags & ~(BPF_F_ADJ_ROOM_FIXED_GSO |
-			       BPF_F_ADJ_ROOM_DECAP_L3_MASK |
+	if (unlikely(flags & ~(BPF_F_ADJ_ROOM_DECAP_MASK |
+			       BPF_F_ADJ_ROOM_FIXED_GSO |
 			       BPF_F_ADJ_ROOM_NO_CSUM_RESET)))
 		return -EINVAL;
 
@@ -3714,8 +3719,7 @@ BPF_CALL_4(bpf_skb_adjust_room, struct sk_buff *, skb, s32, len_diff,
 	u32 off;
 	int ret;
 
-	if (unlikely(flags & ~(BPF_F_ADJ_ROOM_MASK |
-			       BPF_F_ADJ_ROOM_NO_CSUM_RESET)))
+	if (unlikely(flags & ~BPF_F_ADJ_ROOM_MASK))
 		return -EINVAL;
 	if (unlikely(len_diff_abs > 0xfffU))
 		return -EFAULT;
@@ -3734,20 +3738,20 @@ BPF_CALL_4(bpf_skb_adjust_room, struct sk_buff *, skb, s32, len_diff,
 		return -ENOTSUPP;
 	}
 
-	if (flags & BPF_F_ADJ_ROOM_DECAP_L3_MASK) {
+	if (flags & BPF_F_ADJ_ROOM_DECAP_MASK) {
 		if (!shrink)
 			return -EINVAL;
 
-		switch (flags & BPF_F_ADJ_ROOM_DECAP_L3_MASK) {
-		case BPF_F_ADJ_ROOM_DECAP_L3_IPV4:
+		/* Reject mutually exclusive decap flag pairs. */
+		if ((flags & BPF_F_ADJ_ROOM_DECAP_L3_MASK) ==
+		    BPF_F_ADJ_ROOM_DECAP_L3_MASK)
+			return -EINVAL;
+
+		if (flags & BPF_F_ADJ_ROOM_DECAP_L3_IPV4)
 			len_min = sizeof(struct iphdr);
-			break;
-		case BPF_F_ADJ_ROOM_DECAP_L3_IPV6:
+
+		if (flags & BPF_F_ADJ_ROOM_DECAP_L3_IPV6)
 			len_min = sizeof(struct ipv6hdr);
-			break;
-		default:
-			return -EINVAL;
-		}
 	}
 
 	len_cur = skb->len - skb_network_offset(skb);
-- 
2.34.1

[PATCH v6 3/6] bpf: add BPF_F_ADJ_ROOM_DECAP_* flags for tunnel decapsulation

[Nick Hudson]

Add new bpf_skb_adjust_room() decapsulation flags:

- BPF_F_ADJ_ROOM_DECAP_L4_GRE
- BPF_F_ADJ_ROOM_DECAP_L4_UDP
- BPF_F_ADJ_ROOM_DECAP_IPXIP4
- BPF_F_ADJ_ROOM_DECAP_IPXIP6

These flags let BPF programs describe which tunnel layer is being
removed, so later changes can update tunnel-related GSO state
accordingly during decapsulation.

This patch only introduces the UAPI flag definitions and helper
documentation.

Co-developed-by: Max Tottenham <mtottenh@akamai.com>
Signed-off-by: Max Tottenham <mtottenh@akamai.com>
Co-developed-by: Anna Glasgall <aglasgal@akamai.com>
Signed-off-by: Anna Glasgall <aglasgal@akamai.com>
Signed-off-by: Nick Hudson <nhudson@akamai.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
---
 include/uapi/linux/bpf.h       | 34 ++++++++++++++++++++++++++++++++--
 tools/include/uapi/linux/bpf.h | 34 ++++++++++++++++++++++++++++++++--
 2 files changed, 64 insertions(+), 4 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c021ed8d7b44..4a53e731c554 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3010,8 +3010,34 @@ union bpf_attr {
  *
  *		* **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. Used when the inner and outer IP versions are different.
+ *		  Indicate the new IP header version after decapsulating the
+ *		  outer IP header. Used when the inner and outer IP versions
+ *		  are different. These flags only trigger a protocol change
+ *		  without clearing any tunnel-specific GSO flags.
+ *
+ *		* **BPF_F_ADJ_ROOM_DECAP_L4_GRE**:
+ *		  Clear GRE tunnel GSO flags (SKB_GSO_GRE and SKB_GSO_GRE_CSUM)
+ *		  when decapsulating a GRE tunnel.
+ *
+ *		* **BPF_F_ADJ_ROOM_DECAP_L4_UDP**:
+ *		  Clear UDP tunnel GSO flags (SKB_GSO_UDP_TUNNEL and
+ *		  SKB_GSO_UDP_TUNNEL_CSUM) when decapsulating a UDP tunnel.
+ *
+ *		* **BPF_F_ADJ_ROOM_DECAP_IPXIP4**:
+ *		  Clear IPIP/SIT tunnel GSO flag (SKB_GSO_IPXIP4) when decapsulating
+ *		  a tunnel with an outer IPv4 header (IPv4-in-IPv4 or IPv6-in-IPv4).
+ *
+ *		* **BPF_F_ADJ_ROOM_DECAP_IPXIP6**:
+ *		  Clear IPv6 encapsulation tunnel GSO flag (SKB_GSO_IPXIP6) when
+ *		  decapsulating a tunnel with an outer IPv6 header (IPv6-in-IPv6
+ *		  or IPv4-in-IPv6).
+ *
+ *		When using the decapsulation flags above, the skb->encapsulation
+ *		flag is automatically cleared if all tunnel-specific GSO flags
+ *		(SKB_GSO_UDP_TUNNEL, SKB_GSO_UDP_TUNNEL_CSUM, SKB_GSO_GRE,
+ *		SKB_GSO_GRE_CSUM, SKB_GSO_IPXIP4, SKB_GSO_IPXIP6) have been
+ *		removed from the packet. This handles cases where all tunnel
+ *		layers have been decapsulated.
  *
  * 		A call to this helper is susceptible to change the underlying
  * 		packet buffer. Therefore, at load time, all checks on pointers
@@ -6221,6 +6247,10 @@ enum bpf_adj_room_flags {
 	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),
+	BPF_F_ADJ_ROOM_DECAP_L4_GRE	= (1ULL << 9),
+	BPF_F_ADJ_ROOM_DECAP_L4_UDP	= (1ULL << 10),
+	BPF_F_ADJ_ROOM_DECAP_IPXIP4	= (1ULL << 11),
+	BPF_F_ADJ_ROOM_DECAP_IPXIP6	= (1ULL << 12),
 };
 
 enum {
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index ca35ed622ed5..f4c2fbd8fe68 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3010,8 +3010,34 @@ union bpf_attr {
  *
  *		* **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. Used when the inner and outer IP versions are different.
+ *		  Indicate the new IP header version after decapsulating the
+ *		  outer IP header. Used when the inner and outer IP versions
+ *		  are different. These flags only trigger a protocol change
+ *		  without clearing any tunnel-specific GSO flags.
+ *
+ *		* **BPF_F_ADJ_ROOM_DECAP_L4_GRE**:
+ *		  Clear GRE tunnel GSO flags (SKB_GSO_GRE and SKB_GSO_GRE_CSUM)
+ *		  when decapsulating a GRE tunnel.
+ *
+ *		* **BPF_F_ADJ_ROOM_DECAP_L4_UDP**:
+ *		  Clear UDP tunnel GSO flags (SKB_GSO_UDP_TUNNEL and
+ *		  SKB_GSO_UDP_TUNNEL_CSUM) when decapsulating a UDP tunnel.
+ *
+ *		* **BPF_F_ADJ_ROOM_DECAP_IPXIP4**:
+ *		  Clear IPIP/SIT tunnel GSO flag (SKB_GSO_IPXIP4) when decapsulating
+ *		  a tunnel with an outer IPv4 header (IPv4-in-IPv4 or IPv6-in-IPv4).
+ *
+ *		* **BPF_F_ADJ_ROOM_DECAP_IPXIP6**:
+ *		  Clear IPv6 encapsulation tunnel GSO flag (SKB_GSO_IPXIP6) when
+ *		  decapsulating a tunnel with an outer IPv6 header (IPv6-in-IPv6
+ *		  or IPv4-in-IPv6).
+ *
+ *		When using the decapsulation flags above, the skb->encapsulation
+ *		flag is automatically cleared if all tunnel-specific GSO flags
+ *		(SKB_GSO_UDP_TUNNEL, SKB_GSO_UDP_TUNNEL_CSUM, SKB_GSO_GRE,
+ *		SKB_GSO_GRE_CSUM, SKB_GSO_IPXIP4, SKB_GSO_IPXIP6) have been
+ *		removed from the packet. This handles cases where all tunnel
+ *		layers have been decapsulated.
  *
  * 		A call to this helper is susceptible to change the underlying
  * 		packet buffer. Therefore, at load time, all checks on pointers
@@ -6221,6 +6247,10 @@ enum bpf_adj_room_flags {
 	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),
+	BPF_F_ADJ_ROOM_DECAP_L4_GRE	= (1ULL << 9),
+	BPF_F_ADJ_ROOM_DECAP_L4_UDP	= (1ULL << 10),
+	BPF_F_ADJ_ROOM_DECAP_IPXIP4	= (1ULL << 11),
+	BPF_F_ADJ_ROOM_DECAP_IPXIP6	= (1ULL << 12),
 };
 
 enum {
-- 
2.34.1

[PATCH v6 4/6] bpf: allow new DECAP flags and add guard rails

[Nick Hudson]

Add checks to require shrink-only decap, reject conflicting decap flag
combinations, and verify removed length is sufficient for claimed header
decapsulation.

Co-developed-by: Max Tottenham <mtottenh@akamai.com>
Signed-off-by: Max Tottenham <mtottenh@akamai.com>
Co-developed-by: Anna Glasgall <aglasgal@akamai.com>
Signed-off-by: Anna Glasgall <aglasgal@akamai.com>
Signed-off-by: Nick Hudson <nhudson@akamai.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
---
 net/core/filter.c | 44 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 43 insertions(+), 1 deletion(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 02d3947cca32..185a11f425fa 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -56,6 +56,7 @@
 #include <net/sock_reuseport.h>
 #include <net/busy_poll.h>
 #include <net/tcp.h>
+#include <net/gre.h>
 #include <net/xfrm.h>
 #include <net/udp.h>
 #include <linux/bpf_trace.h>
@@ -3484,6 +3485,12 @@ static u32 bpf_skb_net_base_len(const struct sk_buff *skb)
 #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_DECAP_L4_MASK	(BPF_F_ADJ_ROOM_DECAP_L4_UDP | \
+					 BPF_F_ADJ_ROOM_DECAP_L4_GRE)
+
+#define BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK	(BPF_F_ADJ_ROOM_DECAP_IPXIP4 | \
+					 BPF_F_ADJ_ROOM_DECAP_IPXIP6)
+
 #define BPF_F_ADJ_ROOM_ENCAP_MASK	(BPF_F_ADJ_ROOM_ENCAP_L3_MASK | \
 					 BPF_F_ADJ_ROOM_ENCAP_L4_GRE | \
 					 BPF_F_ADJ_ROOM_ENCAP_L4_UDP | \
@@ -3491,7 +3498,9 @@ static u32 bpf_skb_net_base_len(const struct sk_buff *skb)
 					 BPF_F_ADJ_ROOM_ENCAP_L2( \
 					  BPF_ADJ_ROOM_ENCAP_L2_MASK))
 
-#define BPF_F_ADJ_ROOM_DECAP_MASK	(BPF_F_ADJ_ROOM_DECAP_L3_MASK)
+#define BPF_F_ADJ_ROOM_DECAP_MASK	(BPF_F_ADJ_ROOM_DECAP_L3_MASK | \
+					 BPF_F_ADJ_ROOM_DECAP_L4_MASK | \
+					 BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK)
 
 #define BPF_F_ADJ_ROOM_MASK		(BPF_F_ADJ_ROOM_FIXED_GSO | \
 					 BPF_F_ADJ_ROOM_ENCAP_MASK | \
@@ -3739,6 +3748,8 @@ BPF_CALL_4(bpf_skb_adjust_room, struct sk_buff *, skb, s32, len_diff,
 	}
 
 	if (flags & BPF_F_ADJ_ROOM_DECAP_MASK) {
+		u32 len_decap_min = 0;
+
 		if (!shrink)
 			return -EINVAL;
 
@@ -3747,6 +3758,37 @@ BPF_CALL_4(bpf_skb_adjust_room, struct sk_buff *, skb, s32, len_diff,
 		    BPF_F_ADJ_ROOM_DECAP_L3_MASK)
 			return -EINVAL;
 
+		if ((flags & BPF_F_ADJ_ROOM_DECAP_L4_MASK) ==
+		    BPF_F_ADJ_ROOM_DECAP_L4_MASK)
+			return -EINVAL;
+
+		if ((flags & BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK) ==
+		    BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK)
+			return -EINVAL;
+
+		/* Reject mutually exclusive decap tunnel type flags. */
+		if ((flags & BPF_F_ADJ_ROOM_DECAP_L4_MASK) &&
+		    (flags & BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK))
+			return -EINVAL;
+
+		if (flags & BPF_F_ADJ_ROOM_DECAP_L4_MASK)
+			len_decap_min += bpf_skb_net_base_len(skb);
+
+		if (flags & BPF_F_ADJ_ROOM_DECAP_L4_UDP)
+			len_decap_min += sizeof(struct udphdr);
+
+		if (flags & BPF_F_ADJ_ROOM_DECAP_L4_GRE)
+			len_decap_min += sizeof(struct gre_base_hdr);
+
+		if (flags & BPF_F_ADJ_ROOM_DECAP_IPXIP4)
+			len_decap_min += sizeof(struct iphdr);
+
+		if (flags & BPF_F_ADJ_ROOM_DECAP_IPXIP6)
+			len_decap_min += sizeof(struct ipv6hdr);
+
+		if (len_diff_abs < len_decap_min)
+			return -EINVAL;
+
 		if (flags & BPF_F_ADJ_ROOM_DECAP_L3_IPV4)
 			len_min = sizeof(struct iphdr);
 
-- 
2.34.1

[PATCH v6 5/6] bpf: clear decap state on skb_adjust_room shrink path

[Nick Hudson]

On shrink in bpf_skb_adjust_room(), apply decapsulation state updates
according to BPF_F_ADJ_ROOM_DECAP_* flags.

For GSO skbs, clear only the tunnel gso_type bits that correspond to the
requested decap layer:
- DECAP_L4_UDP: SKB_GSO_UDP_TUNNEL{,_CSUM}
- DECAP_L4_GRE: SKB_GSO_GRE{,_CSUM}
- DECAP_IPXIP4: SKB_GSO_IPXIP4
- DECAP_IPXIP6: SKB_GSO_IPXIP6

Then clear skb->encapsulation only if no tunnel GSO bits remain, keeping
encapsulation set for cases such as ESP-in-UDP where tunnel state remains.

For non-GSO skbs, there are no tunnel GSO bits to consult, so clear
skb->encapsulation directly when DECAP_L4_* or DECAP_IPXIP_* flags are set.

This keeps decap state handling consistent between GSO and non-GSO packets.

Co-developed-by: Max Tottenham <mtottenh@akamai.com>
Signed-off-by: Max Tottenham <mtottenh@akamai.com>
Co-developed-by: Anna Glasgall <aglasgal@akamai.com>
Signed-off-by: Anna Glasgall <aglasgal@akamai.com>
Signed-off-by: Nick Hudson <nhudson@akamai.com>
---
 net/core/filter.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/net/core/filter.c b/net/core/filter.c
index 185a11f425fa..3213732dff84 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3666,9 +3666,48 @@ static int bpf_skb_net_shrink(struct sk_buff *skb, u32 off, u32 len_diff,
 		if (!(flags & BPF_F_ADJ_ROOM_FIXED_GSO))
 			skb_increase_gso_size(shinfo, len_diff);
 
+		/* Selective GSO flag clearing based on decap type.
+		 * Only clear the flags for the tunnel layer being removed.
+		 */
+		if ((flags & BPF_F_ADJ_ROOM_DECAP_L4_UDP) &&
+		    (shinfo->gso_type & (SKB_GSO_UDP_TUNNEL |
+					 SKB_GSO_UDP_TUNNEL_CSUM)))
+			shinfo->gso_type &= ~(SKB_GSO_UDP_TUNNEL |
+					      SKB_GSO_UDP_TUNNEL_CSUM);
+		if ((flags & BPF_F_ADJ_ROOM_DECAP_L4_GRE) &&
+		    (shinfo->gso_type & (SKB_GSO_GRE | SKB_GSO_GRE_CSUM)))
+			shinfo->gso_type &= ~(SKB_GSO_GRE |
+					      SKB_GSO_GRE_CSUM);
+		if ((flags & BPF_F_ADJ_ROOM_DECAP_IPXIP4) &&
+		    (shinfo->gso_type & SKB_GSO_IPXIP4))
+			shinfo->gso_type &= ~SKB_GSO_IPXIP4;
+		if ((flags & BPF_F_ADJ_ROOM_DECAP_IPXIP6) &&
+		    (shinfo->gso_type & SKB_GSO_IPXIP6))
+			shinfo->gso_type &= ~SKB_GSO_IPXIP6;
+
+		/* Clear encapsulation flag only when no tunnel GSO flags remain */
+		if (flags & (BPF_F_ADJ_ROOM_DECAP_L4_MASK |
+			     BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK)) {
+			if (!(shinfo->gso_type & (SKB_GSO_UDP_TUNNEL |
+						  SKB_GSO_UDP_TUNNEL_CSUM |
+						  SKB_GSO_GRE |
+						  SKB_GSO_GRE_CSUM |
+						  SKB_GSO_IPXIP4 |
+						  SKB_GSO_IPXIP6 |
+						  SKB_GSO_ESP)))
+				if (skb->encapsulation)
+					skb->encapsulation = 0;
+		}
+
 		/* Header must be checked, and gso_segs recomputed. */
 		shinfo->gso_type |= SKB_GSO_DODGY;
 		shinfo->gso_segs = 0;
+	} else {
+		/* For non-GSO packets, clear encapsulation if decap flags are set */
+		if ((flags & (BPF_F_ADJ_ROOM_DECAP_L4_MASK |
+			      BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK)) &&
+		    skb->encapsulation)
+			skb->encapsulation = 0;
 	}
 
 	return 0;
-- 
2.34.1

[PATCH v6 6/6] selftests/bpf: tc_tunnel - validate decap GSO and encapsulation state

[Nick Hudson]

tc_tunnel only partially validated decap state and missed some tunnel
cases. In particular, IPXIP decap checks were not exercised for
IPIP/SIT paths, and non-GSO decap encapsulation state was not
verified.

Tighten the test by:

- setting DECAP_IPXIP4/6 flags for IPIP/SIT/IP6 decap paths based on
  the outer tunnel header family;
- requiring needed DECAP enum values via CO-RE enum existence checks
  so missing kernel support fails fast;
- validating post-decap tunnel state for both GSO and non-GSO packets:
  expected gso_type bits must be cleared and skb->encapsulation must
  match remaining tunnel flags;
- removing forced TSO disable in the test harness so GSO validation is
  exercised.

This improves coverage for decap tunnel-state regressions and ensures
sit_none/ipip-style paths are checked correctly.

Signed-off-by: Nick Hudson <nhudson@akamai.com>
---
 .../selftests/bpf/prog_tests/test_tc_tunnel.c |  1 -
 .../selftests/bpf/progs/test_tc_tunnel.c      | 91 +++++++++++++++++--
 2 files changed, 84 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/test_tc_tunnel.c b/tools/testing/selftests/bpf/prog_tests/test_tc_tunnel.c
index 1aa7c9463980..67ba27d69347 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_tc_tunnel.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_tc_tunnel.c
@@ -438,7 +438,6 @@ static int setup(void)
 	SYS(fail_close_ns_client, "ip link add %s type veth peer name %s",
 	    "veth1 mtu 1500 netns " CLIENT_NS " address " MAC_ADDR_VETH1,
 	    "veth2 mtu 1500 netns " SERVER_NS " address " MAC_ADDR_VETH2);
-	SYS(fail_close_ns_client, "ethtool -K veth1 tso off");
 	SYS(fail_close_ns_client, "ip link set veth1 up");
 	nstoken_server = open_netns(SERVER_NS);
 	if (!ASSERT_OK_PTR(nstoken_server, "open server ns"))
diff --git a/tools/testing/selftests/bpf/progs/test_tc_tunnel.c b/tools/testing/selftests/bpf/progs/test_tc_tunnel.c
index 7376df405a6b..853bca962910 100644
--- a/tools/testing/selftests/bpf/progs/test_tc_tunnel.c
+++ b/tools/testing/selftests/bpf/progs/test_tc_tunnel.c
@@ -6,6 +6,7 @@
 
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_endian.h>
+#include <bpf/bpf_core_read.h>
 #include "bpf_tracing_net.h"
 #include "bpf_compiler.h"
 
@@ -37,6 +38,22 @@ struct vxlanhdr___local {
 
 #define	EXTPROTO_VXLAN	0x1
 
+#define SKB_GSO_UDP_TUNNEL_MASK	(SKB_GSO_UDP_TUNNEL |			\
+				 SKB_GSO_UDP_TUNNEL_CSUM)
+
+#define SKB_GSO_TUNNEL_MASK	(SKB_GSO_UDP_TUNNEL_MASK |		\
+				 SKB_GSO_GRE |				\
+				 SKB_GSO_GRE_CSUM |			\
+				 SKB_GSO_IPXIP4 |			\
+				 SKB_GSO_IPXIP6 |			\
+				 SKB_GSO_ESP)
+
+#define BPF_F_ADJ_ROOM_DECAP_L4_MASK	(BPF_F_ADJ_ROOM_DECAP_L4_UDP |	\
+					 BPF_F_ADJ_ROOM_DECAP_L4_GRE)
+
+#define BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK	(BPF_F_ADJ_ROOM_DECAP_IPXIP4 |	\
+					 BPF_F_ADJ_ROOM_DECAP_IPXIP6)
+
 #define	VXLAN_FLAGS     bpf_htonl(1<<27)
 #define	VNI_ID		1
 #define	VXLAN_VNI	bpf_htonl(VNI_ID << 8)
@@ -589,9 +606,12 @@ int __encap_ip6vxlan_eth(struct __sk_buff *skb)
 		return TC_ACT_OK;
 }
 
-static int decap_internal(struct __sk_buff *skb, int off, int len, char proto)
+static int decap_internal(struct __sk_buff *skb, int off, int len, char proto,
+			  __u64 ipxip_flag)
 {
 	__u64 flags = BPF_F_ADJ_ROOM_FIXED_GSO;
+	struct sk_buff *kskb;
+	struct skb_shared_info *shinfo;
 	struct ipv6_opt_hdr ip6_opt_hdr;
 	struct gre_hdr greh;
 	struct udphdr udph;
@@ -599,10 +619,12 @@ static int decap_internal(struct __sk_buff *skb, int off, int len, char proto)
 
 	switch (proto) {
 	case IPPROTO_IPIP:
-		flags |= BPF_F_ADJ_ROOM_DECAP_L3_IPV4;
+		flags |= BPF_F_ADJ_ROOM_DECAP_L3_IPV4 |
+			 ipxip_flag;
 		break;
 	case IPPROTO_IPV6:
-		flags |= BPF_F_ADJ_ROOM_DECAP_L3_IPV6;
+		flags |= BPF_F_ADJ_ROOM_DECAP_L3_IPV6 |
+			 ipxip_flag;
 		break;
 	case NEXTHDR_DEST:
 		if (bpf_skb_load_bytes(skb, off + len, &ip6_opt_hdr,
@@ -610,10 +632,12 @@ static int decap_internal(struct __sk_buff *skb, int off, int len, char proto)
 			return TC_ACT_OK;
 		switch (ip6_opt_hdr.nexthdr) {
 		case IPPROTO_IPIP:
-			flags |= BPF_F_ADJ_ROOM_DECAP_L3_IPV4;
+			flags |= BPF_F_ADJ_ROOM_DECAP_L3_IPV4 |
+				 ipxip_flag;
 			break;
 		case IPPROTO_IPV6:
-			flags |= BPF_F_ADJ_ROOM_DECAP_L3_IPV6;
+			flags |= BPF_F_ADJ_ROOM_DECAP_L3_IPV6 |
+				 ipxip_flag;
 			break;
 		default:
 			return TC_ACT_OK;
@@ -621,6 +645,11 @@ static int decap_internal(struct __sk_buff *skb, int off, int len, char proto)
 		break;
 	case IPPROTO_GRE:
 		olen += sizeof(struct gre_hdr);
+		if (!bpf_core_enum_value_exists(enum bpf_adj_room_flags,
+						BPF_F_ADJ_ROOM_DECAP_L4_GRE))
+			return TC_ACT_SHOT;
+		flags |= BPF_F_ADJ_ROOM_DECAP_L4_GRE;
+
 		if (bpf_skb_load_bytes(skb, off + len, &greh, sizeof(greh)) < 0)
 			return TC_ACT_OK;
 		switch (bpf_ntohs(greh.protocol)) {
@@ -634,6 +663,10 @@ static int decap_internal(struct __sk_buff *skb, int off, int len, char proto)
 		break;
 	case IPPROTO_UDP:
 		olen += sizeof(struct udphdr);
+		if (!bpf_core_enum_value_exists(enum bpf_adj_room_flags,
+						BPF_F_ADJ_ROOM_DECAP_L4_UDP))
+			return TC_ACT_SHOT;
+		flags |= BPF_F_ADJ_ROOM_DECAP_L4_UDP;
 		if (bpf_skb_load_bytes(skb, off + len, &udph, sizeof(udph)) < 0)
 			return TC_ACT_OK;
 		switch (bpf_ntohs(udph.dest)) {
@@ -655,6 +688,40 @@ static int decap_internal(struct __sk_buff *skb, int off, int len, char proto)
 	if (bpf_skb_adjust_room(skb, -olen, BPF_ADJ_ROOM_MAC, flags))
 		return TC_ACT_SHOT;
 
+	kskb = bpf_cast_to_kern_ctx(skb);
+	shinfo = bpf_core_cast(kskb->head + kskb->end, struct skb_shared_info);
+	if (shinfo->gso_size) {
+		if ((flags & BPF_F_ADJ_ROOM_DECAP_L4_UDP) &&
+		    (shinfo->gso_type & SKB_GSO_UDP_TUNNEL_MASK))
+			return TC_ACT_SHOT;
+
+		if ((flags & BPF_F_ADJ_ROOM_DECAP_L4_GRE) &&
+		    (shinfo->gso_type & (SKB_GSO_GRE | SKB_GSO_GRE_CSUM)))
+			return TC_ACT_SHOT;
+
+		if ((flags & BPF_F_ADJ_ROOM_DECAP_IPXIP4) &&
+		    (shinfo->gso_type & SKB_GSO_IPXIP4))
+			return TC_ACT_SHOT;
+
+		if ((flags & BPF_F_ADJ_ROOM_DECAP_IPXIP6) &&
+		    (shinfo->gso_type & SKB_GSO_IPXIP6))
+			return TC_ACT_SHOT;
+
+		if (flags & (BPF_F_ADJ_ROOM_DECAP_L4_MASK |
+			     BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK)) {
+			if ((shinfo->gso_type & SKB_GSO_TUNNEL_MASK) &&
+			    !kskb->encapsulation)
+				return TC_ACT_SHOT;
+			if (!(shinfo->gso_type & SKB_GSO_TUNNEL_MASK) &&
+			    kskb->encapsulation)
+				return TC_ACT_SHOT;
+		}
+	} else if ((flags & (BPF_F_ADJ_ROOM_DECAP_L4_MASK |
+			     BPF_F_ADJ_ROOM_DECAP_IPXIP_MASK)) &&
+		   kskb->encapsulation) {
+		return TC_ACT_SHOT;
+	}
+
 	return TC_ACT_OK;
 }
 
@@ -662,6 +729,10 @@ static int decap_ipv4(struct __sk_buff *skb)
 {
 	struct iphdr iph_outer;
 
+	if (!bpf_core_enum_value_exists(enum bpf_adj_room_flags,
+					BPF_F_ADJ_ROOM_DECAP_IPXIP4))
+		return TC_ACT_SHOT;
+
 	if (bpf_skb_load_bytes(skb, ETH_HLEN, &iph_outer,
 			       sizeof(iph_outer)) < 0)
 		return TC_ACT_OK;
@@ -670,19 +741,25 @@ static int decap_ipv4(struct __sk_buff *skb)
 		return TC_ACT_OK;
 
 	return decap_internal(skb, ETH_HLEN, sizeof(iph_outer),
-			      iph_outer.protocol);
+			      iph_outer.protocol,
+			      BPF_F_ADJ_ROOM_DECAP_IPXIP4);
 }
 
 static int decap_ipv6(struct __sk_buff *skb)
 {
 	struct ipv6hdr iph_outer;
 
+	if (!bpf_core_enum_value_exists(enum bpf_adj_room_flags,
+					BPF_F_ADJ_ROOM_DECAP_IPXIP6))
+		return TC_ACT_SHOT;
+
 	if (bpf_skb_load_bytes(skb, ETH_HLEN, &iph_outer,
 			       sizeof(iph_outer)) < 0)
 		return TC_ACT_OK;
 
 	return decap_internal(skb, ETH_HLEN, sizeof(iph_outer),
-			      iph_outer.nexthdr);
+			      iph_outer.nexthdr,
+			      BPF_F_ADJ_ROOM_DECAP_IPXIP6);
 }
 
 SEC("tc")
-- 
2.34.1

Re: [PATCH v6 2/6] bpf: refactor masks for ADJ_ROOM flags and encap validation

[bot+bpf-ci]

[-- Attachment #1: Type: text/plain, Size: 2995 bytes --]

> diff --git a/net/core/filter.c b/net/core/filter.c
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -3484,15 +3484,20 @@ #define BPF_F_ADJ_ROOM_ENCAP_L3_MASK	(BPF_F_ADJ_ROOM_ENCAP_L3_IPV4 | \
>  #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 | \
> +#define BPF_F_ADJ_ROOM_ENCAP_MASK	(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_F_ADJ_ROOM_DECAP_L3_MASK)
> +					  BPF_ADJ_ROOM_ENCAP_L2_MASK))
> +
> +#define BPF_F_ADJ_ROOM_DECAP_MASK	(BPF_F_ADJ_ROOM_DECAP_L3_MASK)
>
> +#define BPF_F_ADJ_ROOM_MASK		(BPF_F_ADJ_ROOM_FIXED_GSO | \
> +					 BPF_F_ADJ_ROOM_ENCAP_MASK | \
> +					 BPF_F_ADJ_ROOM_DECAP_MASK | \
> +					 BPF_F_ADJ_ROOM_NO_CSUM_RESET)
> +
>  static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, u32 len_diff,
>  			    u64 flags)
>  {

[ ... ]

> @@ -3614,8 +3619,8 @@ static int bpf_skb_net_shrink(struct sk_buff *skb, u32 off, u32 len_diff,
>  	bool decap = flags & BPF_F_ADJ_ROOM_DECAP_L3_MASK;
>  	int ret;
>
> -	if (unlikely(flags & ~(BPF_F_ADJ_ROOM_FIXED_GSO |
> -			       BPF_F_ADJ_ROOM_DECAP_L3_MASK |
> +	if (unlikely(flags & ~(BPF_F_ADJ_ROOM_DECAP_MASK |
> +			       BPF_F_ADJ_ROOM_FIXED_GSO |
>  			       BPF_F_ADJ_ROOM_NO_CSUM_RESET)))
>  		return -EINVAL;
>
> @@ -3627,6 +3632,9 @@ static int bpf_skb_net_shrink(struct sk_buff *skb, u32 off, u32 len_diff,
>  	if (decap) {
>  		/* Match skb->protocol to new outer l3 protocol */
>  		if (flags & BPF_F_ADJ_ROOM_DECAP_L3_IPV6)

Martin KaFai Lau raised a concern in v5 about whether non-GSO packets
properly handle decapsulation state clearing when bpf_skb_adjust_room()
is used to decapsulate them. He noted this has been asked multiple
times by AI review bots but has been ignored.

The concern is that BPF programs can call bpf_skb_adjust_room() to
decapsulate non-GSO packets, but if skb->encapsulation remains set after
tunnel headers are stripped, downstream network stack components could
misinterpret the packet as still being encapsulated.

Martin noted that bpf_skb_net_grow() sets encapsulation regardless of
skb_is_gso. Looking at the v6 patch series, the code that handles
decapsulation state still only operates inside the skb_is_gso() block.

Should the decapsulation state clearing logic handle non-GSO packets as
well?

Lore reference: https://lore.kernel.org/bpf/2026427201356.-eYM.martin.lau@linux.dev/
Reviewer: Martin KaFai Lau
Date: Mon, 27 Apr 2026 15:19:53 -0700

[ ... ]


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/25314425016

Re: [PATCH v6 3/6] bpf: add BPF_F_ADJ_ROOM_DECAP_* flags for tunnel decapsulation

[bot+bpf-ci]

[-- Attachment #1: Type: text/plain, Size: 3617 bytes --]

> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index c021ed8d7b44..4a53e731c554 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -3010,8 +3010,34 @@ union bpf_attr {
>   *
>   *		* **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. Used when the inner and outer IP versions are different.
> + *		  Indicate the new IP header version after decapsulating the
> + *		  outer IP header. Used when the inner and outer IP versions
> + *		  are different. These flags only trigger a protocol change
> + *		  without clearing any tunnel-specific GSO flags.
> + *
> + *		* **BPF_F_ADJ_ROOM_DECAP_L4_GRE**:
> + *		  Clear GRE tunnel GSO flags (SKB_GSO_GRE and SKB_GSO_GRE_CSUM)
> + *		  when decapsulating a GRE tunnel.
> + *
> + *		* **BPF_F_ADJ_ROOM_DECAP_L4_UDP**:
> + *		  Clear UDP tunnel GSO flags (SKB_GSO_UDP_TUNNEL and
> + *		  SKB_GSO_UDP_TUNNEL_CSUM) when decapsulating a UDP tunnel.
> + *
> + *		* **BPF_F_ADJ_ROOM_DECAP_IPXIP4**:
> + *		  Clear IPIP/SIT tunnel GSO flag (SKB_GSO_IPXIP4) when decapsulating
> + *		  a tunnel with an outer IPv4 header (IPv4-in-IPv4 or IPv6-in-IPv4).
> + *
> + *		* **BPF_F_ADJ_ROOM_DECAP_IPXIP6**:
> + *		  Clear IPv6 encapsulation tunnel GSO flag (SKB_GSO_IPXIP6) when
> + *		  decapsulating a tunnel with an outer IPv6 header (IPv6-in-IPv6
> + *		  or IPv4-in-IPv6).
> + *
> + *		When using the decapsulation flags above, the skb->encapsulation
> + *		flag is automatically cleared if all tunnel-specific GSO flags
> + *		(SKB_GSO_UDP_TUNNEL, SKB_GSO_UDP_TUNNEL_CSUM, SKB_GSO_GRE,
> + *		SKB_GSO_GRE_CSUM, SKB_GSO_IPXIP4, SKB_GSO_IPXIP6) have been
> + *		removed from the packet. This handles cases where all tunnel
> + *		layers have been decapsulated.

The documentation states that skb->encapsulation is automatically
cleared when all tunnel-specific GSO flags have been removed. Does the
implementation in bpf_skb_net_shrink() handle non-GSO packets correctly?

In v5 review, Martin KaFai Lau noted that the GSO flag clearing logic
is only executed inside the if (skb_is_gso(skb)) block in
bpf_skb_net_shrink(). This means non-GSO packets bypass decapsulation
state clearing. When a non-GSO packet undergoes decapsulation with
tunnel headers stripped but skb->encapsulation remains set, downstream
network stack components may misinterpret the packet as still being
encapsulated.

Note that bpf_skb_net_grow() sets encapsulation regardless of
skb_is_gso, which suggests non-GSO packets can have encapsulation set.

This concern has been raised multiple times by reviewers but has not
been addressed in the current version.

Reference: https://lore.kernel.org/bpf/2026427201356.-eYM.martin.lau@linux.dev/

>   *
>   * 		A call to this helper is susceptible to change the underlying
>   * 		packet buffer. Therefore, at load time, all checks on pointers
> @@ -6221,6 +6247,10 @@ enum bpf_adj_room_flags {
>  	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),
> +	BPF_F_ADJ_ROOM_DECAP_L4_GRE	= (1ULL << 9),
> +	BPF_F_ADJ_ROOM_DECAP_L4_UDP	= (1ULL << 10),
> +	BPF_F_ADJ_ROOM_DECAP_IPXIP4	= (1ULL << 11),
> +	BPF_F_ADJ_ROOM_DECAP_IPXIP6	= (1ULL << 12),
>  };
>
>  enum {

[ ... ]


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/25314425016

Re: [PATCH v6 1/6] bpf: name the enum for BPF_FUNC_skb_adjust_room flags

[bot+bpf-ci]

[-- Attachment #1: Type: text/plain, Size: 1450 bytes --]

> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 552bc5d9afbd..c021ed8d7b44 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -6211,7 +6211,7 @@ enum {
>  };
>
>  /* BPF_FUNC_skb_adjust_room flags. */
> -enum {
> +enum bpf_adj_room_flags {
>  	BPF_F_ADJ_ROOM_FIXED_GSO	= (1ULL << 0),
>  	BPF_F_ADJ_ROOM_ENCAP_L3_IPV4	= (1ULL << 1),
>  	BPF_F_ADJ_ROOM_ENCAP_L3_IPV6	= (1ULL << 2),

Martin KaFai Lau raised a concern in v2 about demonstrating the intended
CO-RE usage, specifically suggesting bpf_core_enum_value_exists():

https://lore.kernel.org/bpf/e5a2ad16-d2ac-4fa0-be41-162227257682@linux.dev/

He also requested that similar tests be added to test_tc_tunnel.c for the
new flags, as was done for earlier BPF_F_ADJ_ROOM_* flag additions.

While v3+ added selftests for decap GSO state validation, does the current
version include tests that explicitly demonstrate the CO-RE enum lookups for
bpf_adj_room_flags that motivated naming this enum?

> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 677be9a47347..ca35ed622ed5 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h

[ ... ]


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/25314425016

Re: [PATCH v6 2/6] bpf: refactor masks for ADJ_ROOM flags and encap validation

[Willem de Bruijn]

Nick Hudson wrote:
> Refactor the helper masks for bpf_skb_adjust_room() flags to simplify
> validation logic and introduce:
> 
> - BPF_F_ADJ_ROOM_ENCAP_MASK
> - BPF_F_ADJ_ROOM_DECAP_MASK
> 
> Refactor existing validation checks in bpf_skb_net_shrink()
> and bpf_skb_adjust_room() to use the new masks (no behavior change).
> 
> This is in preparation for supporting the new decap flags.
> 
> Co-developed-by: Max Tottenham <mtottenh@akamai.com>
> Signed-off-by: Max Tottenham <mtottenh@akamai.com>
> Co-developed-by: Anna Glasgall <aglasgal@akamai.com>
> Signed-off-by: Anna Glasgall <aglasgal@akamai.com>
> Signed-off-by: Nick Hudson <nhudson@akamai.com>

Reviewed-by: Willem de Bruijn <willemb@google.com>

Re: [PATCH v6 5/6] bpf: clear decap state on skb_adjust_room shrink path

[Willem de Bruijn]

Nick Hudson wrote:
> On shrink in bpf_skb_adjust_room(), apply decapsulation state updates
> according to BPF_F_ADJ_ROOM_DECAP_* flags.
> 
> For GSO skbs, clear only the tunnel gso_type bits that correspond to the
> requested decap layer:
> - DECAP_L4_UDP: SKB_GSO_UDP_TUNNEL{,_CSUM}
> - DECAP_L4_GRE: SKB_GSO_GRE{,_CSUM}
> - DECAP_IPXIP4: SKB_GSO_IPXIP4
> - DECAP_IPXIP6: SKB_GSO_IPXIP6
> 
> Then clear skb->encapsulation only if no tunnel GSO bits remain, keeping
> encapsulation set for cases such as ESP-in-UDP where tunnel state remains.
> 
> For non-GSO skbs, there are no tunnel GSO bits to consult, so clear
> skb->encapsulation directly when DECAP_L4_* or DECAP_IPXIP_* flags are set.
> 
> This keeps decap state handling consistent between GSO and non-GSO packets.
> 
> Co-developed-by: Max Tottenham <mtottenh@akamai.com>
> Signed-off-by: Max Tottenham <mtottenh@akamai.com>
> Co-developed-by: Anna Glasgall <aglasgal@akamai.com>
> Signed-off-by: Anna Glasgall <aglasgal@akamai.com>
> Signed-off-by: Nick Hudson <nhudson@akamai.com>

Reviewed-by: Willem de Bruijn <willemb@google.com>