#include #include #include #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