#!/usr/bin/env python3
#
# Copyright (c) 2021 Red Hat, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at:
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# Script information:
# -------------------
# upcall_monitor.py uses the dpif_recv:recv_upcall USDT to receive all upcall
# packets sent by the kernel to ovs-vswitchd. By default, it will show all
# upcall events, which looks something like this:
#
# TIME               CPU  COMM      PID      DPIF_NAME          TYPE PKT_LEN...
# 5952147.003848809  2    handler4  1381158  system@ovs-system  0    98     132
# 5952147.003879643  2    handler4  1381158  system@ovs-system  0    70     160
# 5952147.003914924  2    handler4  1381158  system@ovs-system  0    98     152
#
# In addition, the packet and flow key data can be dumped. This can be done
# using the --packet-decode and --flow-key decode options (see below).
#
# Note that by default only 64 bytes of the packet and flow key are retrieved.
# If you would like to capture all or more of the packet and/or flow key data,
# the ----packet-size and --flow-key-size options can be used.
#
# If required, the received packets can also be stored in a pcap file using the
# --pcap option.
#
# The following are the available options:
#
#    usage: upcall_monitor.py [-h] [-D [DEBUG]] [-d {none,hex,decode}]
#                             [-f [64-2048]] [-k {none,hex,nlraw}]
#                             [-p VSWITCHD_PID] [-s [64-2048]] [-w PCAP_FILE]
#
#    optional arguments:
#      -h, --help            show this help message and exit
#      -D [DEBUG], --debug [DEBUG]
#                            Enable eBPF debugging
#      -d {none,hex,decode}, --packet-decode {none,hex,decode}
#                            Display packet content in selected mode,
#                            default none
#      -f [64-2048], --flow-key-size [64-2048]
#                            Set maximum flow key size to capture, default 64
#      -k {none,hex,nlraw}, --flow-key-decode {none,hex,nlraw}
#                            Display flow-key content in selected mode, default
#                            none
#      -p VSWITCHD_PID, --pid VSWITCHD_PID
#                            ovs-vswitch's PID
#      -s [64-2048], --packet-size [64-2048]
#                            Set maximum packet size to capture, default 64
#      -w PCAP_FILE, --pcap PCAP_FILE
#                            Write upcall packets to specified pcap file.
#
# The following is an example of how to use the script on the running
# ovs-vswitchd process with a packet and flow key dump enabled:
#
#  $ ./upcall_monitor.py --packet-decode decode --flow-key-decode nlraw \
#      --packet-size 128 --flow-key-size 256
#  TIME               CPU  COMM             PID        DPIF_NAME          ...
#  5953013.333214231  2    handler4         1381158    system@ovs-system  ...
#    Flow key size 132 bytes, size captured 132 bytes.
#      nla_len 8, nla_type OVS_KEY_ATTR_RECIRC_ID[20], data: 00 00 00 00
#      nla_len 8, nla_type OVS_KEY_ATTR_DP_HASH[19], data: 00 00 00 00
#      nla_len 8, nla_type OVS_KEY_ATTR_PRIORITY[2], data: 00 00 00 00
#      nla_len 8, nla_type OVS_KEY_ATTR_IN_PORT[3], data: 02 00 00 00
#      nla_len 8, nla_type OVS_KEY_ATTR_SKB_MARK[15], data: 00 00 00 00
#      nla_len 8, nla_type OVS_KEY_ATTR_CT_STATE[22], data: 00 00 00 00
#      nla_len 6, nla_type OVS_KEY_ATTR_CT_ZONE[23], data: 00 00
#      nla_len 8, nla_type OVS_KEY_ATTR_CT_MARK[24], data: 00 00 00 00
#      nla_len 20, nla_type OVS_KEY_ATTR_CT_LABELS[25], data: 00 00 00 00 ...
#      nla_len 16, nla_type OVS_KEY_ATTR_ETHERNET[4], data: 04 f4 bc 28 57 ...
#      nla_len 6, nla_type OVS_KEY_ATTR_ETHERTYPE[6], data: 08 00
#      nla_len 16, nla_type OVS_KEY_ATTR_IPV4[7], data: 01 01 01 64 01 01 ...
#      nla_len 6, nla_type OVS_KEY_ATTR_ICMP[11], data: 00 00
#    1: Receive dp_port 2, packet size 98 bytes, size captured 98 bytes.
#      ###[ Ethernet ]###
#        dst       = 3c:fd:fe:9e:7f:68
#        src       = 04:f4:bc:28:57:01
#        type      = IPv4
#      ###[ IP ]###
#           version   = 4
#           ihl       = 5
#           tos       = 0x0
#           len       = 84
#           id        = 41404
#           flags     = DF
#           frag      = 0
#           ttl       = 64
#           proto     = icmp
#           chksum    = 0x940c
#           src       = 1.1.1.100
#           dst       = 1.1.1.123
#           \options   \
#      ###[ ICMP ]###
#              type      = echo-reply
#              code      = 0
#              chksum    = 0x2f55
#              id        = 0x90e6
#              seq       = 0x1
#      ###[ Raw ]###
#                 load      = 'GBTa\x00\x00\x00\x00\xd8L\r\x00\x00\x00\x00\...
#

from bcc import BPF, USDT, USDTException
from os.path import exists
from scapy.all import hexdump, wrpcap
from scapy.layers.l2 import Ether

import argparse
import psutil
import re
import struct
import sys
import time

#
# Actual eBPF source code
#
ebpf_source = """
#include <linux/sched.h>

#define MAX_PACKET <MAX_PACKET_VAL>
#define MAX_KEY    <MAX_KEY_VAL>

struct event_t {
    u32 cpu;
    u32 pid;
    u32 upcall_type;
    u64 ts;
    u32 pkt_size;
    u64 key_size;
    char comm[TASK_COMM_LEN];
    char dpif_name[32];
    unsigned char pkt[MAX_PACKET];
    unsigned char key[MAX_KEY];
};
BPF_RINGBUF_OUTPUT(events, <BUFFER_PAGE_CNT>);
BPF_TABLE("percpu_array", uint32_t, uint64_t, dropcnt, 1);

int do_trace(struct pt_regs *ctx) {
    uint64_t addr;
    uint64_t size;

    struct event_t *event = events.ringbuf_reserve(sizeof(struct event_t));
    if (!event) {
        uint32_t type = 0;
        uint64_t *value = dropcnt.lookup(&type);
        if (value)
            __sync_fetch_and_add(value, 1);

        return 1;
    }

    event->ts = bpf_ktime_get_ns();
    event->cpu =  bpf_get_smp_processor_id();
    event->pid = bpf_get_current_pid_tgid();
    bpf_get_current_comm(&event->comm, sizeof(event->comm));

    bpf_usdt_readarg(1, ctx, &addr);
    bpf_probe_read_str(&event->dpif_name, sizeof(event->dpif_name),
                       (void *)addr);

    bpf_usdt_readarg(2, ctx, &event->upcall_type);
    bpf_usdt_readarg(4, ctx, &event->pkt_size);
    bpf_usdt_readarg(6, ctx, &event->key_size);

    if (event->pkt_size > MAX_PACKET)
        size = MAX_PACKET;
    else
        size = event->pkt_size;
    bpf_usdt_readarg(3, ctx, &addr);
    bpf_probe_read(&event->pkt, size, (void *)addr);

    if (event->key_size > MAX_KEY)
        size = MAX_KEY;
    else
        size = event->key_size;
    bpf_usdt_readarg(5, ctx, &addr);
    bpf_probe_read(&event->key, size, (void *)addr);

    events.ringbuf_submit(event, 0);
    return 0;
};
"""


#
# print_event()
#
def print_event(ctx, data, size):
    event = b['events'].event(data)
    print("{:<18.9f} {:<4} {:<16} {:<10} {:<32} {:<4} {:<10} {:<10}".
          format(event.ts / 1000000000,
                 event.cpu,
                 event.comm.decode("utf-8"),
                 event.pid,
                 event.dpif_name.decode("utf-8"),
                 event.upcall_type,
                 event.pkt_size,
                 event.key_size))

    #
    # Dump flow key information
    #
    if event.key_size < options.flow_key_size:
        key_len = event.key_size
    else:
        key_len = options.flow_key_size

    if options.flow_key_decode != 'none':
        print("  Flow key size {} bytes, size captured {} bytes.".
              format(event.key_size, key_len))

    if options.flow_key_decode == 'hex':
        #
        # Abuse scapy's hex dump to dump flow key
        #
        print(re.sub('^', ' ' * 4, hexdump(Ether(bytes(event.key)[:key_len]),
                                           dump=True),
                     flags=re.MULTILINE))

    if options.flow_key_decode == 'nlraw':
        nla = decode_nlm(bytes(event.key)[:key_len])
    else:
        nla = decode_nlm(bytes(event.key)[:key_len], dump=False)

    if "OVS_KEY_ATTR_IN_PORT" in nla:
        port = struct.unpack("=I", nla["OVS_KEY_ATTR_IN_PORT"])[0]
    else:
        port = "Unknown"

    #
    # Decode packet only if there is data
    #
    if event.pkt_size <= 0:
        return

    pkt_id = get_pkt_id()

    if event.pkt_size < options.packet_size:
        pkt_len = event.pkt_size
        pkt_data = bytes(event.pkt)[:event.pkt_size]
    else:
        pkt_len = options.packet_size
        pkt_data = bytes(event.pkt)

    if options.packet_decode != 'none' or options.pcap is not None:
        print("  {}: Receive dp_port {}, packet size {} bytes, size "
              "captured {} bytes.".format(pkt_id, port, event.pkt_size,
                                          pkt_len))

    if options.packet_decode == 'hex':
        print(re.sub('^', ' ' * 4, hexdump(pkt_data, dump=True),
                     flags=re.MULTILINE))

    packet = Ether(pkt_data)
    packet.wirelen = event.pkt_size

    if options.packet_decode == 'decode':
        print(re.sub('^', ' ' * 4, packet.show(dump=True), flags=re.MULTILINE))

    if options.pcap is not None:
        wrpcap(options.pcap, packet, append=True, snaplen=options.packet_size)


#
# decode_nlm()
#
def decode_nlm(msg, indent=4, dump=True):
    bytes_left = len(msg)
    result = {}

    while bytes_left:
        if bytes_left < 4:
            if dump:
                print("{}WARN: decode truncated; can't read header".format(
                    ' ' * indent))
            break

        nla_len, nla_type = struct.unpack("=HH", msg[:4])

        if nla_len < 4:
            if dump:
                print("{}WARN: decode truncated; nla_len < 4".format(
                    ' ' * indent))
            break

        nla_data = msg[4:nla_len]
        trunc = ""

        if nla_len > bytes_left:
            trunc = "..."
            nla_data = nla_data[:(bytes_left - 4)]
        else:
            result[get_ovs_key_attr_str(nla_type)] = nla_data

        if dump:
            print("{}nla_len {}, nla_type {}[{}], data: {}{}".format(
                ' ' * indent, nla_len, get_ovs_key_attr_str(nla_type),
                nla_type,
                "".join("{:02x} ".format(b) for b in nla_data), trunc))

        if trunc != "":
            if dump:
                print("{}WARN: decode truncated; nla_len > msg_len[{}] ".
                      format(' ' * indent, bytes_left))
            break

        # update next offset, but make sure it's aligned correctly
        next_offset = (nla_len + 3) & ~(3)
        msg = msg[next_offset:]
        bytes_left -= next_offset

    return result


#
# get_ovs_key_attr_str()
#
def get_ovs_key_attr_str(attr):
    ovs_key_attr = ["OVS_KEY_ATTR_UNSPEC",
                    "OVS_KEY_ATTR_ENCAP",
                    "OVS_KEY_ATTR_PRIORITY",
                    "OVS_KEY_ATTR_IN_PORT",
                    "OVS_KEY_ATTR_ETHERNET",
                    "OVS_KEY_ATTR_VLAN",
                    "OVS_KEY_ATTR_ETHERTYPE",
                    "OVS_KEY_ATTR_IPV4",
                    "OVS_KEY_ATTR_IPV6",
                    "OVS_KEY_ATTR_TCP",
                    "OVS_KEY_ATTR_UDP",
                    "OVS_KEY_ATTR_ICMP",
                    "OVS_KEY_ATTR_ICMPV6",
                    "OVS_KEY_ATTR_ARP",
                    "OVS_KEY_ATTR_ND",
                    "OVS_KEY_ATTR_SKB_MARK",
                    "OVS_KEY_ATTR_TUNNEL",
                    "OVS_KEY_ATTR_SCTP",
                    "OVS_KEY_ATTR_TCP_FLAGS",
                    "OVS_KEY_ATTR_DP_HASH",
                    "OVS_KEY_ATTR_RECIRC_ID",
                    "OVS_KEY_ATTR_MPLS",
                    "OVS_KEY_ATTR_CT_STATE",
                    "OVS_KEY_ATTR_CT_ZONE",
                    "OVS_KEY_ATTR_CT_MARK",
                    "OVS_KEY_ATTR_CT_LABELS",
                    "OVS_KEY_ATTR_CT_ORIG_TUPLE_IPV4",
                    "OVS_KEY_ATTR_CT_ORIG_TUPLE_IPV6",
                    "OVS_KEY_ATTR_NSH"]

    if attr < 0 or attr > len(ovs_key_attr):
        return "<UNKNOWN>"

    return ovs_key_attr[attr]


#
# get_pkt_id()
#
def get_pkt_id():
    if not hasattr(get_pkt_id, "counter"):
        get_pkt_id.counter = 0
    get_pkt_id.counter += 1
    return get_pkt_id.counter


#
# buffer_size_type()
#
def buffer_size_type(astr, min=64, max=2048):
    value = int(astr)
    if min <= value <= max:
        return value
    else:
        raise argparse.ArgumentTypeError(
            'value not in range {}-{}'.format(min, max))


#
# next_power_of_two()
#
def next_power_of_two(val):
    np = 1
    while np < val:
        np *= 2
    return np


#
# main()
#
def main():
    #
    # Don't like these globals, but ctx passing does not seem to work with the
    # existing open_ring_buffer() API :(
    #
    global b
    global options

    #
    # Argument parsing
    #
    parser = argparse.ArgumentParser()

    parser.add_argument("--buffer-page-count",
                        help="Number of BPF ring buffer pages, default 1024",
                        type=int, default=1024, metavar="NUMBER")
    parser.add_argument("-D", "--debug",
                        help="Enable eBPF debugging",
                        type=int, const=0x3f, default=0, nargs='?')
    parser.add_argument('-d', '--packet-decode',
                        help='Display packet content in selected mode, '
                        'default none',
                        choices=['none', 'hex', 'decode'], default='none')
    parser.add_argument("-f", "--flow-key-size",
                        help="Set maximum flow key size to capture, "
                        "default 64", type=buffer_size_type, default=64,
                        metavar="[64-2048]")
    parser.add_argument('-k', '--flow-key-decode',
                        help='Display flow-key content in selected mode, '
                        'default none',
                        choices=['none', 'hex', 'nlraw'], default='none')
    parser.add_argument("-p", "--pid", metavar="VSWITCHD_PID",
                        help="ovs-vswitch's PID",
                        type=int, default=None)
    parser.add_argument("-s", "--packet-size",
                        help="Set maximum packet size to capture, "
                        "default 64", type=buffer_size_type, default=64,
                        metavar="[64-2048]")
    parser.add_argument("-w", "--pcap", metavar="PCAP_FILE",
                        help="Write upcall packets to specified pcap file.",
                        type=str, default=None)

    options = parser.parse_args()

    #
    # Find the PID of the ovs-vswitchd daemon if not specified.
    #
    if options.pid is None:
        for proc in psutil.process_iter():
            if 'ovs-vswitchd' in proc.name():
                if options.pid is not None:
                    print("ERROR: Multiple ovs-vswitchd daemons running, "
                          "use the -p option!")
                    sys.exit(-1)

                options.pid = proc.pid

    #
    # Error checking on input parameters
    #
    if options.pid is None:
        print("ERROR: Failed to find ovs-vswitchd's PID!")
        sys.exit(-1)

    if options.pcap is not None:
        if exists(options.pcap):
            print("ERROR: Destination capture file \"{}\" already exists!".
                  format(options.pcap))
            sys.exit(-1)

    options.buffer_page_count = next_power_of_two(options.buffer_page_count)

    #
    # Attach the usdt probe
    #
    u = USDT(pid=int(options.pid))
    try:
        u.enable_probe(probe="recv_upcall", fn_name="do_trace")
    except USDTException as e:
        print("ERROR: {}"
              "ovs-vswitchd!".format(
                  (re.sub('^', ' ' * 7, str(e), flags=re.MULTILINE)).strip().
                  replace("--with-dtrace or --enable-dtrace",
                          "--enable-usdt-probes")))
        sys.exit(-1)

    #
    # Uncomment to see how arguments are decoded.
    #   print(u.get_text())
    #

    #
    # Attach probe to running process
    #
    source = ebpf_source.replace("<MAX_PACKET_VAL>", str(options.packet_size))
    source = source.replace("<MAX_KEY_VAL>", str(options.flow_key_size))
    source = source.replace("<BUFFER_PAGE_CNT>",
                            str(options.buffer_page_count))

    b = BPF(text=source, usdt_contexts=[u], debug=options.debug)

    #
    # Print header
    #
    print("{:<18} {:<4} {:<16} {:<10} {:<32} {:<4} {:<10} {:<10}".format(
        "TIME", "CPU", "COMM", "PID", "DPIF_NAME", "TYPE", "PKT_LEN",
        "FLOW_KEY_LEN"))

    #
    # Dump out all events
    #
    b['events'].open_ring_buffer(print_event)
    while 1:
        try:
            b.ring_buffer_poll()
            time.sleep(0.5)
        except KeyboardInterrupt:
            break

    dropcnt = b.get_table("dropcnt")
    for k in dropcnt.keys():
        count = dropcnt.sum(k).value
        if k.value == 0 and count > 0:
            print("\nWARNING: Not all upcalls were captured, {} were dropped!"
                  "\n         Increase the BPF ring buffer size with the "
                  "--buffer-page-count option.".format(count))


#
# Start main() as the default entry point...
#
if __name__ == '__main__':
    main()