From: Cong Wang <cong.wang@xxxxxxxxxxxxx>
Similarly to the previous test, we also need a test case to cover
positive offsets as well, TC is an excellent hook for this.
Cc: John Fastabend <john.fastabend@xxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Tested-by: Zijian Zhang <zijianzhang@xxxxxxxxxxxxx>
Signed-off-by: Cong Wang <cong.wang@xxxxxxxxxxxxx>
---
.../selftests/bpf/prog_tests/tc_change_tail.c | 62 ++++++++++
.../selftests/bpf/progs/test_tc_change_tail.c | 106 ++++++++++++++++++
2 files changed, 168 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/tc_change_tail.c
create mode 100644 tools/testing/selftests/bpf/progs/test_tc_change_tail.c
diff --git a/tools/testing/selftests/bpf/prog_tests/tc_change_tail.c b/tools/testing/selftests/bpf/prog_tests/tc_change_tail.c
new file mode 100644
index 000000000000..74752233e779
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/tc_change_tail.c
@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <error.h>
+#include <test_progs.h>
+#include <linux/pkt_cls.h>
+
+#include "test_tc_change_tail.skel.h"
+#include "socket_helpers.h"
+
+#define LO_IFINDEX 1
+
+void test_tc_change_tail(void)
+{
+ LIBBPF_OPTS(bpf_tcx_opts, tcx_opts);
+ struct test_tc_change_tail *skel = NULL;
+ struct bpf_link *link;
+ int c1, p1;
+ char buf[2];
+ int ret;
+
+ skel = test_tc_change_tail__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "test_tc_change_tail__open_and_load"))
+ return;
+
+ link = bpf_program__attach_tcx(skel->progs.change_tail, LO_IFINDEX,
+ &tcx_opts);
+ if (!ASSERT_OK_PTR(link, "bpf_program__attach_tcx"))
+ goto destroy;
+
+ skel->links.change_tail = link;
+ ret = create_pair(AF_INET, SOCK_DGRAM, &c1, &p1);
+ if (!ASSERT_OK(ret, "create_pair"))
+ goto destroy;
+
+ ret = xsend(p1, "Tr", 2, 0);
+ ASSERT_EQ(ret, 2, "xsend(p1)");
+ ret = recv(c1, buf, 2, 0);
+ ASSERT_EQ(ret, 2, "recv(c1)");
+ ASSERT_EQ(skel->data->change_tail_ret, 0, "change_tail_ret");
+
+ ret = xsend(p1, "G", 1, 0);
+ ASSERT_EQ(ret, 1, "xsend(p1)");
+ ret = recv(c1, buf, 2, 0);
+ ASSERT_EQ(ret, 1, "recv(c1)");
+ ASSERT_EQ(skel->data->change_tail_ret, 0, "change_tail_ret");
+
+ ret = xsend(p1, "E", 1, 0);
+ ASSERT_EQ(ret, 1, "xsend(p1)");
+ ret = recv(c1, buf, 1, 0);
+ ASSERT_EQ(ret, 1, "recv(c1)");
+ ASSERT_EQ(skel->data->change_tail_ret, -EINVAL, "change_tail_ret");
+
+ ret = xsend(p1, "Z", 1, 0);
+ ASSERT_EQ(ret, 1, "xsend(p1)");
+ ret = recv(c1, buf, 1, 0);
+ ASSERT_EQ(ret, 1, "recv(c1)");
+ ASSERT_EQ(skel->data->change_tail_ret, -EINVAL, "change_tail_ret");
+
+ close(c1);
+ close(p1);
+destroy:
+ test_tc_change_tail__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_tc_change_tail.c b/tools/testing/selftests/bpf/progs/test_tc_change_tail.c
new file mode 100644
index 000000000000..28edafe803f0
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_tc_change_tail.c
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <linux/if_ether.h>
+#include <linux/in.h>
+#include <linux/ip.h>
+#include <linux/udp.h>
+#include <linux/pkt_cls.h>
+
+long change_tail_ret = 1;
+
+static __always_inline struct iphdr *parse_ip_header(struct __sk_buff *skb, int *ip_proto)
+{
+ void *data_end = (void *)(long)skb->data_end;
+ void *data = (void *)(long)skb->data;
+ struct ethhdr *eth = data;
+ struct iphdr *iph;
+
+ /* Verify Ethernet header */
+ if ((void *)(data + sizeof(*eth)) > data_end)
+ return NULL;
+
+ /* Skip Ethernet header to get to IP header */
+ iph = (void *)(data + sizeof(struct ethhdr));
+
+ /* Verify IP header */
+ if ((void *)(data + sizeof(struct ethhdr) + sizeof(*iph)) > data_end)
+ return NULL;
+
+ /* Basic IP header validation */
+ if (iph->version != 4) /* Only support IPv4 */
+ return NULL;
+
+ if (iph->ihl < 5) /* Minimum IP header length */
+ return NULL;
+
+ *ip_proto = iph->protocol;
+ return iph;
+}
+
+static __always_inline struct udphdr *parse_udp_header(struct __sk_buff *skb, struct iphdr *iph)
+{
+ void *data_end = (void *)(long)skb->data_end;
+ void *hdr = (void *)iph;
+ struct udphdr *udp;
+
+ /* Calculate UDP header position */
+ udp = hdr + (iph->ihl * 4);
+ hdr = (void *)udp;
+
+ /* Verify UDP header bounds */
+ if ((void *)(hdr + sizeof(*udp)) > data_end)
+ return NULL;
+
+ return udp;
+}
+
+SEC("tc/ingress")
+int change_tail(struct __sk_buff *skb)
+{
+ int len = skb->len;
+ struct udphdr *udp;
+ struct iphdr *iph;
+ void *data_end;
+ char *payload;
+ int ip_proto;
+
+ bpf_skb_pull_data(skb, len);
+
+ data_end = (void *)(long)skb->data_end;
+ iph = parse_ip_header(skb, &ip_proto);
+ if (!iph)
+ return TCX_PASS;
+
+ if (ip_proto != IPPROTO_UDP)
+ return TCX_PASS;
+
+ udp = parse_udp_header(skb, iph);
+ if (!udp)
+ return TCX_PASS;
+
+ payload = (char *)udp + (sizeof(struct udphdr));
+ if (payload + 1 > (char *)data_end)
+ return TCX_PASS;
+
+ if (payload[0] == 'T') { /* Trim the packet */
+ change_tail_ret = bpf_skb_change_tail(skb, len - 1, 0);
+ if (!change_tail_ret)
+ bpf_skb_change_tail(skb, len, 0);
+ return TCX_PASS;
+ } else if (payload[0] == 'G') { /* Grow the packet */
+ change_tail_ret = bpf_skb_change_tail(skb, len + 1, 0);
+ if (!change_tail_ret)
+ bpf_skb_change_tail(skb, len, 0);
+ return TCX_PASS;
+ } else if (payload[0] == 'E') { /* Error */
+ change_tail_ret = bpf_skb_change_tail(skb, 65535, 0);
+ return TCX_PASS;
+ } else if (payload[0] == 'Z') { /* Zero */
+ change_tail_ret = bpf_skb_change_tail(skb, 0, 0);
+ return TCX_PASS;
+ }
+ return TCX_DROP;
+}
+
+char _license[] SEC("license") = "GPL";
--
2.34.1
