5 files changed, 299 insertions, 0 deletions

diff --git a/bpf/filter/bpf.c b/bpf/filter/bpf.c
new file mode 100644
index 0000000..ae62cb8
--- /dev/null
+++ b/bpf/filter/bpf.c
@@ -0,0 +1,82 @@
+#include <linux/bpf.h>
+#include <linux/if_ether.h>
+#include <linux/ip.h>
+
+#include <bpf/bpf_endian.h>
+#include <bpf/bpf_helpers.h>
+
+#define MAX_MAP_ENTRIES 4096
+
+char __license[] SEC("license") = "GPL";
+
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(max_entries, MAX_MAP_ENTRIES);
+	__type(key, __u64);  // blocked mac address
+	// i just like her for the o(1) key lookup
+	// we don't care about the value
+	__type(value, __u16); 
+} mac_blacklist_map SEC(".maps");
+
+static __always_inline __u64 nchar6_to_u64(unsigned char bytes[6])
+{
+	union {
+		char bytes[6];
+		__u64 i;
+	} ret;
+
+	ret.i = 0;
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+	ret.bytes[0] = bytes[5];
+	ret.bytes[1] = bytes[4];
+	ret.bytes[2] = bytes[3];
+	ret.bytes[3] = bytes[2];
+	ret.bytes[4] = bytes[1];
+	ret.bytes[5] = bytes[0];
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+	ret.bytes[0] = bytes[0];
+	ret.bytes[1] = bytes[1];
+	ret.bytes[2] = bytes[2];
+	ret.bytes[3] = bytes[3];
+	ret.bytes[4] = bytes[4];
+	ret.bytes[5] = bytes[5];
+#endif
+
+	return ret.i;
+}
+
+static __always_inline int mac_src_parse(struct xdp_md *ctx, __u64 *mac)
+{
+	__u64 len, *usage;
+
+	void *data_end = (void *)(long)ctx->data_end;
+	struct ethhdr *eth = (void *)(long)ctx->data;
+
+	if ((void *) (eth + 1) > data_end)
+		return -1;
+
+	if (eth->h_proto != bpf_htons(ETH_P_IP) &&
+	    eth->h_proto != bpf_htons(ETH_P_IPV6)) {
+		return -1;
+	}
+
+	*mac = nchar6_to_u64(eth->h_source);
+	return 0;
+}
+
+SEC("xdp")
+int mac_filter(struct xdp_md *ctx)
+{
+	__u64 mac;
+	int ret, *blocked;
+
+	ret = mac_src_parse(ctx, &mac);
+	if (ret < 0)
+		return XDP_PASS;
+
+	blocked = bpf_map_lookup_elem(&mac_blacklist_map, &mac);
+	if (blocked)
+		return XDP_DROP;
+
+	return XDP_PASS;
+}
diff --git a/bpf/filter/bpf_bpfel.go b/bpf/filter/bpf_bpfel.go
new file mode 100644
index 0000000..53ec23f
--- /dev/null
+++ b/bpf/filter/bpf_bpfel.go
@@ -0,0 +1,119 @@
+// Code generated by bpf2go; DO NOT EDIT.
+//go:build 386 || amd64 || arm || arm64 || loong64 || mips64le || mipsle || ppc64le || riscv64
+
+package filter
+
+import (
+	"bytes"
+	_ "embed"
+	"fmt"
+	"io"
+
+	"github.com/cilium/ebpf"
+)
+
+// loadBpf returns the embedded CollectionSpec for bpf.
+func loadBpf() (*ebpf.CollectionSpec, error) {
+	reader := bytes.NewReader(_BpfBytes)
+	spec, err := ebpf.LoadCollectionSpecFromReader(reader)
+	if err != nil {
+		return nil, fmt.Errorf("can't load bpf: %w", err)
+	}
+
+	return spec, err
+}
+
+// loadBpfObjects loads bpf and converts it into a struct.
+//
+// The following types are suitable as obj argument:
+//
+//	*bpfObjects
+//	*bpfPrograms
+//	*bpfMaps
+//
+// See ebpf.CollectionSpec.LoadAndAssign documentation for details.
+func loadBpfObjects(obj interface{}, opts *ebpf.CollectionOptions) error {
+	spec, err := loadBpf()
+	if err != nil {
+		return err
+	}
+
+	return spec.LoadAndAssign(obj, opts)
+}
+
+// bpfSpecs contains maps and programs before they are loaded into the kernel.
+//
+// It can be passed ebpf.CollectionSpec.Assign.
+type bpfSpecs struct {
+	bpfProgramSpecs
+	bpfMapSpecs
+}
+
+// bpfSpecs contains programs before they are loaded into the kernel.
+//
+// It can be passed ebpf.CollectionSpec.Assign.
+type bpfProgramSpecs struct {
+	MacFilter *ebpf.ProgramSpec `ebpf:"mac_filter"`
+}
+
+// bpfMapSpecs contains maps before they are loaded into the kernel.
+//
+// It can be passed ebpf.CollectionSpec.Assign.
+type bpfMapSpecs struct {
+	MacBlacklistMap *ebpf.MapSpec `ebpf:"mac_blacklist_map"`
+}
+
+// bpfObjects contains all objects after they have been loaded into the kernel.
+//
+// It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign.
+type bpfObjects struct {
+	bpfPrograms
+	bpfMaps
+}
+
+func (o *bpfObjects) Close() error {
+	return _BpfClose(
+		&o.bpfPrograms,
+		&o.bpfMaps,
+	)
+}
+
+// bpfMaps contains all maps after they have been loaded into the kernel.
+//
+// It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign.
+type bpfMaps struct {
+	MacBlacklistMap *ebpf.Map `ebpf:"mac_blacklist_map"`
+}
+
+func (m *bpfMaps) Close() error {
+	return _BpfClose(
+		m.MacBlacklistMap,
+	)
+}
+
+// bpfPrograms contains all programs after they have been loaded into the kernel.
+//
+// It can be passed to loadBpfObjects or ebpf.CollectionSpec.LoadAndAssign.
+type bpfPrograms struct {
+	MacFilter *ebpf.Program `ebpf:"mac_filter"`
+}
+
+func (p *bpfPrograms) Close() error {
+	return _BpfClose(
+		p.MacFilter,
+	)
+}
+
+func _BpfClose(closers ...io.Closer) error {
+	for _, closer := range closers {
+		if err := closer.Close(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Do not access this directly.
+//
+//go:embed bpf_bpfel.o
+var _BpfBytes []byte
diff --git a/bpf/filter/bpf_bpfel.o b/bpf/filter/bpf_bpfel.o
new file mode 100644
index 0000000..2167b99
--- /dev/null
+++ b/bpf/filter/bpf_bpfel.o
diff --git a/bpf/filter/gen.go b/bpf/filter/gen.go
new file mode 100644
index 0000000..d70c549
--- /dev/null
+++ b/bpf/filter/gen.go
@@ -0,0 +1,3 @@
+package filter
+
+//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -target bpfel bpf bpf.c
diff --git a/bpf/filter/main.go b/bpf/filter/main.go
new file mode 100644
index 0000000..4df312c
--- /dev/null
+++ b/bpf/filter/main.go
@@ -0,0 +1,95 @@
+package filter
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"net"
+
+	"github.com/cilium/ebpf/link"
+	"sinanmohd.com/redq/db"
+)
+
+type Filter struct {
+	ctxDb context.Context
+	queries *db.Queries
+	objs bpfObjects
+	xdpLink link.Link
+}
+
+func Close(f *Filter) {
+	f.objs.Close()
+	f.xdpLink.Close()
+}
+
+func New(iface *net.Interface, queries *db.Queries, ctxDb context.Context) (*Filter, error) {
+	var err error
+	var f Filter
+
+	if err := loadBpfObjects(&f.objs, nil); err != nil {
+		log.Printf("loading objects: %s", err)
+		return nil, err
+	}
+	defer func() {
+		if err != nil {
+			f.objs.Close()
+		}
+	}()
+
+	f.xdpLink, err = link.AttachXDP(link.XDPOptions{
+		Interface: iface.Index,
+		Program:   f.objs.MacFilter,
+	})
+	if err != nil {
+		log.Printf("could not attach TCx program: %s", err)
+		return nil, err
+	}
+	defer func() {
+		if err != nil {
+			f.xdpLink.Close()
+		}
+	}()
+
+	blackList, err := queries.GetMacBlackList(ctxDb)
+	zeros := make([]uint16, len(blackList))
+	_, err = f.objs.bpfMaps.MacBlacklistMap.BatchUpdate(blackList[:], zeros, nil)
+	if err != nil {
+		log.Printf("loading mac blacklist: %s", err)
+		return nil, err
+	}
+
+	f.queries = queries
+	return &f, nil
+}
+
+func (f *Filter) Block(mac uint64) error {
+	err := f.queries.EnterMacBlackList(f.ctxDb, int64(mac))
+	if err != nil {
+		log.Printf("adding mac blacklist: %s", err)
+		return err
+	}
+
+	err = f.objs.bpfMaps.MacBlacklistMap.Put(mac, true)
+	if err != nil {
+		log.Printf("adding mac blacklist: %s", err)
+		return err
+	}
+
+	return nil
+}
+
+func (f *Filter) Unblock(mac uint64) error {
+	err := f.queries.DeleteDnsBlackList(f.ctxDb, fmt.Sprintf("%v", mac))
+	if err != nil {
+		log.Printf("adding mac blacklist: %s", err)
+		return err
+	}
+
+	err = f.objs.bpfMaps.MacBlacklistMap.Delete(mac)
+	if err != nil {
+		log.Printf("adding mac blacklist: %s", err)
+		return err
+	}
+
+	return nil
+}