diff options
Diffstat (limited to 'xdp_udp_handler.c')
-rw-r--r-- | xdp_udp_handler.c | 127 |
1 files changed, 127 insertions, 0 deletions
diff --git a/xdp_udp_handler.c b/xdp_udp_handler.c new file mode 100644 index 0000000..930667f --- /dev/null +++ b/xdp_udp_handler.c @@ -0,0 +1,127 @@ +#include <linux/bpf.h> +#include <linux/in.h> + +#include <bpf/bpf_helpers.h> + +#include "xdp_checksum.h" +#include "xdp_manip.h" +#include "xdp_parser.h" + +#ifdef XDP_DEBUG +#define dbg_bpf_printk(fmt, args...) bpf_printk(fmt, ##args) +#else +#define dbg_bpf_printk(fmt, args...) +#endif + +#include "common.h" + +SEC("xdp") +int xdp_udp_handler(struct xdp_md *ctx) { + void *data_end = (void *)(long)ctx->data_end; + void *data = (void *)(long)ctx->data; + __u32 action = XDP_PASS; /* Default action */ + struct hdr_cursor nh = {.pos = data}; + int nh_type; + struct ethhdr *ethhdr; + struct iphdr *iphdr = NULL; + struct ipv6hdr *ip6hdr = NULL; + struct udphdr *udphdr; + static const __u8 payload_request[] = {PAYLOAD_REQUEST}; + static const __u32 payload_request_size = sizeof(payload_request); + static const __u8 payload_response[] = {PAYLOAD_RESPONSE}; + __u32 payload_size; + + nh_type = parse_ethhdr(&nh, data_end, ðhdr); + + switch (__constant_ntohs(nh_type)) { + case ETH_P_IP: + nh_type = parse_iphdr(&nh, data_end, &iphdr); + break; + case ETH_P_IPV6: + nh_type = parse_ip6hdr(&nh, data_end, &ip6hdr); + break; + default: + goto out; + } + + if (nh_type != IPPROTO_UDP) { + goto out; + } + if (parse_udphdr(&nh, data_end, &udphdr) < 0) { + action = XDP_ABORTED; + goto out; + } + if (udphdr->dest != __constant_htons(UDP_PORT)) { + goto out; + } + + payload_size = (__u8 *)data_end - (__u8 *)nh.pos; + if (payload_size < payload_request_size) { + goto out; + } + + if (nh.pos_u8 + payload_request_size + 1 > (__u8 *)data_end) { + goto out; + } + if (__builtin_memcmp(nh.pos_u8, payload_request, sizeof(payload_request)) != + 0) { + goto out; + } + + dbg_bpf_printk("Received UDP Ping Request #%u with size %u", nh.pos_u8[11], + payload_size); + + /* Shrink UDP packet for Ping Reply */ + if (bpf_xdp_adjust_tail(ctx, payload_request_size - payload_size) != 0) { + return XDP_ABORTED; + } + + /* Set data pointers (may not be valid anymore) */ + data = (void *)(long)ctx->data; + data_end = (void *)(long)ctx->data_end; + nh.pos = data; + + if (parse_ethhdr(&nh, data_end, ðhdr) < 0) { + action = XDP_ABORTED; + goto out; + } + + payload_size -= 4; + + if (iphdr != NULL) { + if (parse_iphdr(&nh, data_end, &iphdr) < 0) { + action = XDP_ABORTED; + goto out; + } + if (parse_udphdr(&nh, data_end, &udphdr) < 0) { + action = XDP_ABORTED; + goto out; + } + swap_eth_addr(ethhdr); + udphdr->len = __constant_htons(payload_size + sizeof(*udphdr)); + iphdr->tot_len = + __constant_htons(iphdr->ihl * 4 + payload_size + sizeof(*udphdr)); + swap_ip4_addr(iphdr); + iphdr->check = ip_checksum(iphdr); + if (nh.pos_u8 + sizeof(payload_response) > (__u8 *)data_end) { + action = XDP_ABORTED; + goto out; + } + __builtin_memcpy(nh.pos_u8, payload_response, sizeof(payload_response)); + swap_udp_port(udphdr); + udphdr->check = udp_checksum(iphdr, udphdr, data_end); + } else if (ip6hdr != NULL) { + parse_ip6hdr(&nh, data_end, &ip6hdr); + goto out; // TODO: Implement! + } else { + action = XDP_ABORTED; + goto out; + } + + action = XDP_TX; +out: + return action; +} + +char _license[] SEC("license") = + "GPL"; // Please keep this to prevent tainting kernel |