Question

我从here获得了代码。

from binascii import hexlify
from ctypes import create_string_buffer, addressof
from socket import socket, AF_PACKET, SOCK_RAW, SOL_SOCKET
from struct import pack, unpack

sniff_interval=120
# A subset of Berkeley Packet Filter constants and macros, as defined in
# linux/filter.h.

# Instruction classes
BPF_LD = 0x00
BPF_JMP = 0x05
BPF_RET = 0x06

# ld/ldx fields
BPF_H = 0x08
BPF_B = 0x10
BPF_ABS = 0x20

# alu/jmp fields
BPF_JEQ = 0x10
BPF_K = 0x00

def bpf_jump(code, k, jt, jf):
    return pack('HBBI', code, jt, jf, k)

def bpf_stmt(code, k):
    return bpf_jump(code, k, 0, 0)


# Ordering of the filters is backwards of what would be intuitive for
# performance reasons: the check that is most likely to fail is first.
filters_list = [
    # Must have dst port 67. Load (BPF_LD) a half word value (BPF_H) in
    # ethernet frame at absolute byte offset 36 (BPF_ABS). If value is equal to
    # 67 then do not jump, else jump 5 statements.
    bpf_stmt(BPF_LD | BPF_H | BPF_ABS, 36),
    bpf_jump(BPF_JMP | BPF_JEQ | BPF_K, 5201, 0, 5),

    # Must be UDP (check protocol field at byte offset 23)
    bpf_stmt(BPF_LD | BPF_B | BPF_ABS, 23),
    bpf_jump(BPF_JMP | BPF_JEQ | BPF_K, 0x06, 0, 3),

    # Must be IPv4 (check ethertype field at byte offset 12)
    bpf_stmt(BPF_LD | BPF_H | BPF_ABS, 12),
    bpf_jump(BPF_JMP | BPF_JEQ | BPF_K, 0x0800, 0, 1),

    bpf_stmt(BPF_RET | BPF_K, 0x0fffffff), # pass
    bpf_stmt(BPF_RET | BPF_K, 0), # reject
]

# Create filters struct and fprog struct to be used by SO_ATTACH_FILTER, as
# defined in linux/filter.h.
filters = ''.join(filters_list)
b = create_string_buffer(filters)
mem_addr_of_filters = addressof(b)
fprog = pack('HL', len(filters_list), mem_addr_of_filters)

# As defined in asm/socket.h
SO_ATTACH_FILTER = 26

# Create listening socket with filters
s = socket(AF_PACKET, SOCK_RAW, 0x0800)
s.setsockopt(SOL_SOCKET, SO_ATTACH_FILTER, fprog)
s.bind(('eth0', 0x0800))

while True:
    data, addr = s.recvfrom(65565)
    #print "*****"
    print 'got data from', addr, ':', hexlify(data) #Have to print data, then only the CPU is 2%

我正在使用iperf3进行测试，通过以太网线将另一台笔记本电脑的流量传输到我的笔记本电脑。在5021上列出的服务器（我的笔记本电脑）和发送数据的客户端（另一台笔记本电脑）

如果我评论行print 'got data from', addr, ':', hexlify(data)，并运行脚本，脚本的CPU利用率在100MB流量的情况下，上涨30％，40％。
如果我取消注释行print 'got data from', addr, ':', hexlify(data)并再次运行，则CPU会在存在相同数量的流量时降至2%。我签到了 htop

那么，什么在这里讨厌？

Answer 1

我敢打赌hexlify()，或者最有可能print（因为它必须与STDOUT同步）正在为你的主线程提供一个急需的休息时间和一个呼吸的空间而不仅仅是冲击套接字在无限while循环中读出

首先尝试添加time.sleep(0.05)（首先导入time）而不是print语句，然后再次检查CPU使用情况。

我使用BPF过滤器时python脚本的CPU利用率

1 个答案: