diff options
Diffstat (limited to 'tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt_dynptr.c')
-rw-r--r-- | tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt_dynptr.c | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt_dynptr.c b/tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt_dynptr.c new file mode 100644 index 000000000000..d3b319722e30 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_parse_tcp_hdr_opt_dynptr.c @@ -0,0 +1,114 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* This logic is lifted from a real-world use case of packet parsing, used in + * the open source library katran, a layer 4 load balancer. + * + * This test demonstrates how to parse packet contents using dynptrs. The + * original code (parsing without dynptrs) can be found in test_parse_tcp_hdr_opt.c + */ + +#include <linux/bpf.h> +#include <bpf/bpf_helpers.h> +#include <linux/tcp.h> +#include <stdbool.h> +#include <linux/ipv6.h> +#include <linux/if_ether.h> +#include "test_tcp_hdr_options.h" +#include "bpf_kfuncs.h" + +char _license[] SEC("license") = "GPL"; + +/* Kind number used for experiments */ +const __u32 tcp_hdr_opt_kind_tpr = 0xFD; +/* Length of the tcp header option */ +const __u32 tcp_hdr_opt_len_tpr = 6; +/* maximum number of header options to check to lookup server_id */ +const __u32 tcp_hdr_opt_max_opt_checks = 15; + +__u32 server_id; + +static int parse_hdr_opt(struct bpf_dynptr *ptr, __u32 *off, __u8 *hdr_bytes_remaining, + __u32 *server_id) +{ + __u8 *tcp_opt, kind, hdr_len; + __u8 buffer[sizeof(kind) + sizeof(hdr_len) + sizeof(*server_id)]; + __u8 *data; + + __builtin_memset(buffer, 0, sizeof(buffer)); + + data = bpf_dynptr_slice(ptr, *off, buffer, sizeof(buffer)); + if (!data) + return -1; + + kind = data[0]; + + if (kind == TCPOPT_EOL) + return -1; + + if (kind == TCPOPT_NOP) { + *off += 1; + *hdr_bytes_remaining -= 1; + return 0; + } + + if (*hdr_bytes_remaining < 2) + return -1; + + hdr_len = data[1]; + if (hdr_len > *hdr_bytes_remaining) + return -1; + + if (kind == tcp_hdr_opt_kind_tpr) { + if (hdr_len != tcp_hdr_opt_len_tpr) + return -1; + + __builtin_memcpy(server_id, (__u32 *)(data + 2), sizeof(*server_id)); + return 1; + } + + *off += hdr_len; + *hdr_bytes_remaining -= hdr_len; + return 0; +} + +SEC("xdp") +int xdp_ingress_v6(struct xdp_md *xdp) +{ + __u8 buffer[sizeof(struct tcphdr)] = {}; + __u8 hdr_bytes_remaining; + struct tcphdr *tcp_hdr; + __u8 tcp_hdr_opt_len; + int err = 0; + __u32 off; + + struct bpf_dynptr ptr; + + bpf_dynptr_from_xdp(xdp, 0, &ptr); + + off = sizeof(struct ethhdr) + sizeof(struct ipv6hdr); + + tcp_hdr = bpf_dynptr_slice(&ptr, off, buffer, sizeof(buffer)); + if (!tcp_hdr) + return XDP_DROP; + + tcp_hdr_opt_len = (tcp_hdr->doff * 4) - sizeof(struct tcphdr); + if (tcp_hdr_opt_len < tcp_hdr_opt_len_tpr) + return XDP_DROP; + + hdr_bytes_remaining = tcp_hdr_opt_len; + + off += sizeof(struct tcphdr); + + /* max number of bytes of options in tcp header is 40 bytes */ + for (int i = 0; i < tcp_hdr_opt_max_opt_checks; i++) { + err = parse_hdr_opt(&ptr, &off, &hdr_bytes_remaining, &server_id); + + if (err || !hdr_bytes_remaining) + break; + } + + if (!server_id) + return XDP_DROP; + + return XDP_PASS; +} |