85 lines
2.3 KiB
Go
85 lines
2.3 KiB
Go
// This program demonstrates attaching an eBPF program to a network interface
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// with XDP (eXpress Data Path). The program parses the IPv4 source address
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// from packets and writes the packet count by IP to an LRU hash map.
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// The userspace program (Go code in this file) prints the contents
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// of the map to stdout every second.
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// It is possible to modify the XDP program to drop or redirect packets
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// as well -- give it a try!
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// This example depends on bpf_link, available in Linux kernel version 5.7 or newer.
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package main
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import (
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"fmt"
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"log"
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"net"
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"os"
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"strings"
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"time"
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"github.com/cilium/ebpf"
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"github.com/cilium/ebpf/link"
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)
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// $BPF_CLANG and $BPF_CFLAGS are set by the Makefile.
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//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -cc $BPF_CLANG -cflags $BPF_CFLAGS bpf xdp.c -- -I../headers
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func main() {
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if len(os.Args) < 2 {
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log.Fatalf("Please specify a network interface")
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}
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// Look up the network interface by name.
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ifaceName := os.Args[1]
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iface, err := net.InterfaceByName(ifaceName)
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if err != nil {
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log.Fatalf("lookup network iface %q: %s", ifaceName, err)
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}
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// Load pre-compiled programs into the kernel.
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objs := bpfObjects{}
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if err := loadBpfObjects(&objs, nil); err != nil {
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log.Fatalf("loading objects: %s", err)
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}
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defer objs.Close()
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// Attach the program.
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l, err := link.AttachXDP(link.XDPOptions{
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Program: objs.XdpProgFunc,
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Interface: iface.Index,
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})
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if err != nil {
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log.Fatalf("could not attach XDP program: %s", err)
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}
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defer l.Close()
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log.Printf("Attached XDP program to iface %q (index %d)", iface.Name, iface.Index)
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log.Printf("Press Ctrl-C to exit and remove the program")
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// Print the contents of the BPF hash map (source IP address -> packet count).
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ticker := time.NewTicker(1 * time.Second)
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defer ticker.Stop()
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for range ticker.C {
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s, err := formatMapContents(objs.XdpStatsMap)
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if err != nil {
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log.Printf("Error reading map: %s", err)
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continue
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}
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log.Printf("Map contents:\n%s", s)
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}
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}
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func formatMapContents(m *ebpf.Map) (string, error) {
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var (
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sb strings.Builder
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key []byte
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val uint32
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)
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iter := m.Iterate()
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for iter.Next(&key, &val) {
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sourceIP := net.IP(key) // IPv4 source address in network byte order.
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packetCount := val
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sb.WriteString(fmt.Sprintf("\t%s => %d\n", sourceIP, packetCount))
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}
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return sb.String(), iter.Err()
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}
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