selftests/bpf: tc_tunnel - pass decap flags for tunnel type

commit-author Nick Hudson <nhudson@akamai.com>
commit -
commit-source https://lore.kernel.org/netdev/20260504101759.3319427-7-nhudson@akamai.com/
upstream-diff |
  The upstream patch targets a newer selftest framework with CO-RE
  support (bpf_cast_to_kern_ctx, bpf_core_cast, bpf_core_enum_value_exists).
  This tree has an older version of test_tc_tunnel.c without those
  features, so the following upstream changes were dropped:
  - CO-RE enum existence checks for flag availability
  - Post-decap GSO gso_type and skb->encapsulation validation
  - TSO disable removal from prog_tests/test_tc_tunnel.c (file absent)
  The functional flag-passing changes (DECAP_L4_GRE, DECAP_L4_UDP,
  DECAP_IPXIP4, DECAP_IPXIP6) to decap_internal/decap_ipv4/decap_ipv6
  are applied as in upstream.

Pass the new BPF_F_ADJ_ROOM_DECAP_* flags through the decap path so
the kernel clears the correct GSO and encapsulation state when removing
tunnel headers.

	Signed-off-by: Nick Hudson <nhudson@akamai.com>
	Signed-off-by: Brett Mastbergen <bmastbergen@ciq.com>

Author: bmastbergen

tools/testing/selftests/bpf/progs/test_tc_tunnel.c

@@ -597,7 +597,8 @@ 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 ipv6_opt_hdr ip6_opt_hdr;
@@ -607,28 +608,33 @@ 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,
 				       sizeof(ip6_opt_hdr)) < 0)
 			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;
 		}
 		break;
 	case IPPROTO_GRE:
 		olen += sizeof(struct gre_hdr);
+		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)) {
@@ -642,6 +648,7 @@ static int decap_internal(struct __sk_buff *skb, int off, int len, char proto)
 		break;
 	case IPPROTO_UDP:
 		olen += sizeof(struct udphdr);
+		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)) {
@@ -678,7 +685,8 @@ 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)
@@ -690,7 +698,8 @@ static int decap_ipv6(struct __sk_buff *skb)
 		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("decap")