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54 lines
1.3 KiB
C
54 lines
1.3 KiB
C
// xdp_lb.bpf.c
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#include <linux/bpf.h>
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#include <bpf/bpf_helpers.h>
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#include <linux/if_ether.h>
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#include <linux/ip.h>
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#include <linux/in.h>
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struct {
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__uint(type, BPF_MAP_TYPE_ARRAY);
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__uint(max_entries, 2); // Two backends
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__type(key, __u32);
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__type(value, __u32); // Backend IPs
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} backends SEC(".maps");
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SEC("xdp")
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int xdp_load_balancer(struct xdp_md *ctx) {
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void *data_end = (void *)(long)ctx->data_end;
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void *data = (void *)(long)ctx->data;
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struct ethhdr *eth = data;
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if ((void *)(eth + 1) > data_end)
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return XDP_PASS;
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if (eth->h_proto != __constant_htons(ETH_P_IP))
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return XDP_PASS;
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struct iphdr *iph = (struct iphdr *)(eth + 1);
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if ((void *)(iph + 1) > data_end)
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return XDP_PASS;
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if (iph->protocol != IPPROTO_TCP && iph->protocol != IPPROTO_UDP)
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return XDP_PASS;
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__u32 key = 0;
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static __u32 cnt = 0;
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__u32 *backend_ip = bpf_map_lookup_elem(&backends, &key);
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if (!backend_ip)
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return XDP_PASS;
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cnt = (cnt + 1) % 2; // Round-robin
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key = cnt;
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backend_ip = bpf_map_lookup_elem(&backends, &key);
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if (backend_ip) {
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iph->daddr = *backend_ip; // Redirect to the backend IP
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iph->check = 0; // Needs recomputation in real cases
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}
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return XDP_TX; // Transmit modified packet back
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}
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char _license[] SEC("license") = "GPL";
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