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Output TCP flags alongside tuple #466

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Output TCP flags alongside tuple #466

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3 changes: 2 additions & 1 deletion bpf/kprobe_pwru.c
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Original file line number Diff line number Diff line change
Expand Up @@ -64,7 +64,7 @@ struct tuple {
u16 dport;
u16 l3_proto;
u8 l4_proto;
u8 pad;
u8 tcp_flags;
} __attribute__((packed));

enum event_type {
Expand Down Expand Up @@ -311,6 +311,7 @@ __set_tuple(struct tuple *tpl, void *data, u16 l3_off, bool is_ipv4) {
struct tcphdr *tcp = (struct tcphdr *) (data + l4_off);
tpl->sport= BPF_CORE_READ(tcp, source);
tpl->dport= BPF_CORE_READ(tcp, dest);
bpf_probe_read_kernel(&tpl->tcp_flags, sizeof(tpl->tcp_flags), (void *)tcp + offsetof(struct tcphdr, window) - 1);
} else if (tpl->l4_proto == IPPROTO_UDP) {
struct udphdr *udp = (struct udphdr *) (data + l4_off);
tpl->sport= BPF_CORE_READ(udp, source);
Expand Down
14 changes: 11 additions & 3 deletions internal/pwru/output.go
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Original file line number Diff line number Diff line change
Expand Up @@ -76,6 +76,7 @@ type jsonTuple struct {
Sport uint16 `json:"sport,omitempty"`
Dport uint16 `json:"dport,omitempty"`
Proto uint8 `json:"proto,omitempty"`
Flags string `json:"flags,omitempty"`
}

func centerAlignString(s string, width int) string {
Expand All @@ -100,7 +101,7 @@ func NewOutput(flags *Flags, printSkbMap, printShinfoMap, printStackMap *ebpf.Ma

reasons, err := getKFreeSKBReasons(btfSpec)
if err != nil {
log.Printf("Unable to load packet drop reaons: %v", err)
log.Printf("Unable to load packet drop reasons: %v", err)
}

var ifs map[uint64]map[uint32]string
Expand Down Expand Up @@ -203,6 +204,7 @@ func (o *output) PrintJson(event *Event) {
t.Sport = byteorder.NetworkToHost16(event.Tuple.Sport)
t.Dport = byteorder.NetworkToHost16(event.Tuple.Dport)
t.Proto = event.Tuple.L4Proto
t.Flags = event.Tuple.TCPFlag.String()
d.Tuple = t
}

Expand Down Expand Up @@ -271,10 +273,16 @@ func getAddrByArch(event *Event, o *output) (addr uint64) {
}

func getTupleData(event *Event) (tupleData string) {
var l4Info string
if event.Tuple.L4Proto == syscall.IPPROTO_TCP && event.Tuple.TCPFlag != 0 {
l4Info = fmt.Sprintf("%s:%s", protoToStr(event.Tuple.L4Proto), event.Tuple.TCPFlag)
} else {
l4Info = protoToStr(event.Tuple.L4Proto)
}
tupleData = fmt.Sprintf("%s:%d->%s:%d(%s)",
addrToStr(event.Tuple.L3Proto, event.Tuple.Saddr), byteorder.NetworkToHost16(event.Tuple.Sport),
addrToStr(event.Tuple.L3Proto, event.Tuple.Daddr), byteorder.NetworkToHost16(event.Tuple.Dport),
protoToStr(event.Tuple.L4Proto))
l4Info)
return tupleData
}

Expand Down Expand Up @@ -498,7 +506,7 @@ func addrToStr(proto uint16, addr [16]byte) string {
}
}

// getKFreeSKBReasons dervices SKB drop reasons from the "skb_drop_reason" enum
// getKFreeSKBReasons derives SKB drop reasons from the "skb_drop_reason" enum
// defined in /include/net/dropreason.h.
func getKFreeSKBReasons(spec *btf.Spec) (map[uint64]string, error) {
if _, err := spec.AnyTypeByName("kfree_skb_reason"); err != nil {
Expand Down
26 changes: 25 additions & 1 deletion internal/pwru/types.go
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Original file line number Diff line number Diff line change
Expand Up @@ -115,14 +115,38 @@ func (f *Flags) Parse() {
}
}

type tcpFlag uint8

func (f tcpFlag) String() string {
tcpFlags := []string{
"FIN",
"SYN",
"RST",
"PSH",
"ACK",
"URG",
"ECE",
"CWR",
}

var flags []string
for i, flag := range tcpFlags {
if f&(1<<uint(i)) != 0 {
flags = append(flags, flag)
}
}

return strings.Join(flags, "|")
}

type Tuple struct {
Saddr [16]byte
Daddr [16]byte
Sport uint16
Dport uint16
L3Proto uint16
L4Proto uint8
Pad uint8
TCPFlag tcpFlag
}

type Meta struct {
Expand Down
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