hyp/hypd/server/hyp_bpf.c
Steven Polley b318bcb3c1
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continuous-integration/drone/push Build is passing
invert conditionals, removing crazy nesting
Thank you code aesthetic
2024-05-09 20:17:02 -06:00

75 lines
1.8 KiB
C

/*
Copyright © 2024 Steven Polley <himself@stevenpolley.net>
*/
//go:build ignore
#include "vmlinux.h"
#include "bpf_endian.h"
#include <bpf/bpf_helpers.h>
char __license[] SEC("license") = "BSD";
// representation of knock data that gets sent to userspace
struct knock_data {
__u32 srcip; // 4 bytes
__u16 dstport; // 2 bytes
__u16 pad; // required padding - struct must be multiple of 4 bytes
};
// ring buffer used to send data to userspace
struct {
__uint(type, BPF_MAP_TYPE_RINGBUF);
__uint(max_entries, 1 << 24);
} rb SEC(".maps");
// force emitting struct event into the ELF
const struct knock_data *unused __attribute__((unused));
// hook into xpress data path attach point
SEC("xdp")
int xdp_prog_func(struct xdp_md *ctx) {
// xdp gives us the raw frame with no structures, it must be parsed
void *data = (void *)(long)ctx->data;
void *data_end = (void *)(long)ctx->data_end;
// A knock should not contain any data
if (data_end - data > 60) {
return XDP_PASS;
}
// parse ethernet header
struct ethhdr *eth = data;
if ((void *)eth + sizeof(*eth) > data_end) {
return XDP_PASS;
}
// parse IP header
struct iphdr *ip = data + sizeof(*eth);
if ((void *)ip + sizeof(*ip) > data_end) {
return XDP_PASS;
}
// Ensure IP header protocol field is UDP (protocol 17)
if (ip->protocol != IPPROTO_UDP) {
return XDP_PASS;
}
// parse UDP header
struct udphdr *udp = (void *)ip + sizeof(*ip);
if ((void *)udp + sizeof(*udp) > data_end) {
return XDP_PASS;
}
// pack into knock structure and send to userspace
struct knock_data knock = {
.srcip = bpf_ntohl(ip->saddr),
.dstport = bpf_htons(udp->dest),
.pad = 0
};
bpf_ringbuf_output(&rb, &knock, sizeof(knock), BPF_RB_FORCE_WAKEUP);
// We send everything to XDP_PASS
return XDP_PASS;
}