每隔几天我就会遇到以下问题。我的笔记本电脑（经过Debian测试）突然变得无法使用与Internet的TCP连接。
以下内容可以正常运行：
- UDP（DNS），ICMP（ping）—我得到即时响应
- 与局域网中其他计算机的TCP连接（例如，我可以ssh到邻居笔记本电脑）
- 局域网中的其他机器一切正常
但是，当我尝试从笔记本电脑进行TCP连接时，它们会超时（对SYN数据包无响应）。这是典型的curl输出：
% curl -v google.com
* About to connect() to google.com port 80 (#0)
* Trying 173.194.39.105...
* Connection timed out
* Trying 173.194.39.110...
* Connection timed out
* Trying 173.194.39.97...
* Connection timed out
* Trying 173.194.39.102...
* Timeout
* Trying 173.194.39.98...
* Timeout
* Trying 173.194.39.96...
* Timeout
* Trying 173.194.39.103...
* Timeout
* Trying 173.194.39.99...
* Timeout
* Trying 173.194.39.101...
* Timeout
* Trying 173.194.39.104...
* Timeout
* Trying 173.194.39.100...
* Timeout
* Trying 2a00:1450:400d:803::1009...
* Failed to connect to 2a00:1450:400d:803::1009: Network is unreachable
* Success
* couldn't connect to host
* Closing connection #0
curl: (7) Failed to connect to 2a00:1450:400d:803::1009: Network is unreachable
重新启动连接和/或重新加载网卡内核模块无济于事。唯一有用的是重新启动。
显然我的系统出了点问题（其他所有东西都可以正常工作），但我不知道到底是什么。
我的设置是通过PPPoE连接到ISP的无线路由器。
有什么建议吗？
评论的答案
这是什么网卡？
12:00.0 Network controller: Broadcom Corporation BCM4313 802.11b/g/n Wireless LAN Controller (rev 01)
Subsystem: Dell Inspiron M5010 / XPS 8300
Flags: bus master, fast devsel, latency 0, IRQ 17
Memory at fbb00000 (64-bit, non-prefetchable) [size=16K]
Capabilities: [40] Power Management version 3
Capabilities: [58] Vendor Specific Information: Len=78 <?>
Capabilities: [48] MSI: Enable- Count=1/1 Maskable- 64bit+
Capabilities: [d0] Express Endpoint, MSI 00
Capabilities: [100] Advanced Error Reporting
Capabilities: [13c] Virtual Channel
Capabilities: [160] Device Serial Number 00-00-9d-ff-ff-aa-1c-65
Capabilities: [16c] Power Budgeting <?>
Kernel driver in use: brcmsmac
出现问题时，NIC的状态是什么？
iptables-save 什么都不打印。
ip rule show：
0: from all lookup local
32766: from all lookup main
32767: from all lookup default
ip route show table all：
default via 192.168.1.1 dev wlan0
192.168.1.0/24 dev wlan0 proto kernel scope link src 192.168.1.105
broadcast 127.0.0.0 dev lo table local proto kernel scope link src 127.0.0.1
local 127.0.0.0/8 dev lo table local proto kernel scope host src 127.0.0.1
local 127.0.0.1 dev lo table local proto kernel scope host src 127.0.0.1
broadcast 127.255.255.255 dev lo table local proto kernel scope link src 127.0.0.1
broadcast 192.168.1.0 dev wlan0 table local proto kernel scope link src 192.168.1.105
local 192.168.1.105 dev wlan0 table local proto kernel scope host src 192.168.1.105
broadcast 192.168.1.255 dev wlan0 table local proto kernel scope link src 192.168.1.105
fe80::/64 dev wlan0 proto kernel metric 256
unreachable default dev lo table unspec proto kernel metric 4294967295 error -101 hoplimit 255
local ::1 via :: dev lo table local proto none metric 0
local fe80::1e65:9dff:feaa:b1f1 via :: dev lo table local proto none metric 0
ff00::/8 dev wlan0 table local metric 256
unreachable default dev lo table unspec proto kernel metric 4294967295 error -101 hoplimit 255
当机器在正常模式下工作时，以上所有内容均相同。
ifconfig—我运行了它，但是以某种方式忘记了保存，然后重新启动。将不得不等到下一次出现问题。对于那个很抱歉。
是否有任何QoS？
可能不是-至少我没有做任何专门的事情来启用它。
您是否尝试嗅探接口上实际发送的流量？
我多次运行curl和tcpdump，有两种模式。
第一个只是没有答案的SYN数据包。
17:14:37.836917 IP (tos 0x0, ttl 64, id 4563, offset 0, flags [DF], proto TCP (6), length 60)
192.168.1.105.42030 > fra07s07-in-f102.1e100.net.http: Flags [S], cksum 0x27fc (incorrect -> 0xbea8), seq 3764607647, win 13600, options [mss 1360,sackOK,TS val 33770316 ecr 0,nop,wscale 4], length 0
17:14:38.836650 IP (tos 0x0, ttl 64, id 4564, offset 0, flags [DF], proto TCP (6), length 60)
192.168.1.105.42030 > fra07s07-in-f102.1e100.net.http: Flags [S], cksum 0x27fc (incorrect -> 0xbdae), seq 3764607647, win 13600, options [mss 1360,sackOK,TS val 33770566 ecr 0,nop,wscale 4], length 0
17:14:40.840649 IP (tos 0x0, ttl 64, id 4565, offset 0, flags [DF], proto TCP (6), length 60)
192.168.1.105.42030 > fra07s07-in-f102.1e100.net.http: Flags [S], cksum 0x27fc (incorrect -> 0xbbb9), seq 3764607647, win 13600, options [mss 1360,sackOK,TS val 33771067 ecr 0,nop,wscale 4], length 0
第二个是这样的：
17:22:56.507827 IP (tos 0x0, ttl 64, id 41583, offset 0, flags [DF], proto TCP (6), length 60)
192.168.1.105.42036 > fra07s07-in-f102.1e100.net.http: Flags [S], cksum 0x27fc (incorrect -> 0x2244), seq 1564709704, win 13600, options [mss 1360,sackOK,TS val 33894944 ecr 0,nop,wscale 4], length 0
17:22:56.546763 IP (tos 0x58, ttl 54, id 65442, offset 0, flags [none], proto TCP (6), length 60)
fra07s07-in-f102.1e100.net.http > 192.168.1.105.42036: Flags [S.], cksum 0x6b1e (correct), seq 1407776542, ack 1564709705, win 14180, options [mss 1430,sackOK,TS val 3721836586 ecr 33883552,nop,wscale 6], length 0
17:22:56.546799 IP (tos 0x58, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 40)
192.168.1.105.42036 > fra07s07-in-f102.1e100.net.http: Flags [R], cksum 0xf301 (correct), seq 1564709705, win 0, length 0
17:22:58.511843 IP (tos 0x0, ttl 64, id 41584, offset 0, flags [DF], proto TCP (6), length 60)
192.168.1.105.42036 > fra07s07-in-f102.1e100.net.http: Flags [S], cksum 0x27fc (incorrect -> 0x204f), seq 1564709704, win 13600, options [mss 1360,sackOK,TS val 33895445 ecr 0,nop,wscale 4], length 0
17:22:58.555423 IP (tos 0x58, ttl 54, id 65443, offset 0, flags [none], proto TCP (6), length 60)
fra07s07-in-f102.1e100.net.http > 192.168.1.105.42036: Flags [S.], cksum 0x3b03 (correct), seq 1439178112, ack 1564709705, win 14180, options [mss 1430,sackOK,TS val 3721838596 ecr 33883552,nop,wscale 6], length 0
17:22:58.555458 IP (tos 0x58, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 40)
192.168.1.105.42036 > fra07s07-in-f102.1e100.net.http: Flags [R], cksum 0xf301 (correct), seq 1564709705, win 0, length 0
ethtool输出
ethtool -k wlan0：
Features for wlan0:
rx-checksumming: off [fixed]
tx-checksumming: off
tx-checksum-ipv4: off [fixed]
tx-checksum-unneeded: off [fixed]
tx-checksum-ip-generic: off [fixed]
tx-checksum-ipv6: off [fixed]
tx-checksum-fcoe-crc: off [fixed]
tx-checksum-sctp: off [fixed]
scatter-gather: off
tx-scatter-gather: off [fixed]
tx-scatter-gather-fraglist: off [fixed]
tcp-segmentation-offload: off
tx-tcp-segmentation: off [fixed]
tx-tcp-ecn-segmentation: off [fixed]
tx-tcp6-segmentation: off [fixed]
udp-fragmentation-offload: off [fixed]
generic-segmentation-offload: off [requested on]
generic-receive-offload: on
large-receive-offload: off [fixed]
rx-vlan-offload: off [fixed]
tx-vlan-offload: off [fixed]
ntuple-filters: off [fixed]
receive-hashing: off [fixed]
highdma: off [fixed]
rx-vlan-filter: off [fixed]
vlan-challenged: off [fixed]
tx-lockless: off [fixed]
netns-local: on [fixed]
tx-gso-robust: off [fixed]
tx-fcoe-segmentation: off [fixed]
fcoe-mtu: off [fixed]
tx-nocache-copy: off
loopback: off [fixed]
iptables
# namei -l "$(command -v iptables)"
f: /sbin/iptables
drwxr-xr-x root root /
drwxr-xr-x root root sbin
lrwxrwxrwx root root iptables -> xtables-multi
-rwxr-xr-x root root xtables-multi
# dpkg -S "$(command -v iptables)"
iptables: /sbin/iptables
# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
# iptables -t mangle -nvL
Chain PREROUTING (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain POSTROUTING (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
# iptables -t nat -nvL
Chain PREROUTING (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain POSTROUTING (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
# iptables -t security -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
模块信息
# ethtool -i wlan0
driver: brcmsmac
version: 3.2.0-3-686-pae
firmware-version: N/A
bus-info: 0000:12:00.0
supports-statistics: no
supports-test: no
supports-eeprom-access: no
supports-register-dump: no
supports-priv-flags: no
# modinfo brcmsmac
filename: /lib/modules/3.2.0-3-686-pae/kernel/drivers/net/wireless/brcm80211/brcmsmac/brcmsmac.ko
license: Dual BSD/GPL
description: Broadcom 802.11n wireless LAN driver.
author: Broadcom Corporation
alias: pci:v000014E4d00000576sv*sd*bc*sc*i*
alias: pci:v000014E4d00004727sv*sd*bc*sc*i*
alias: pci:v000014E4d00004353sv*sd*bc*sc*i*
alias: pci:v000014E4d00004357sv*sd*bc*sc*i*
depends: mac80211,brcmutil,cfg80211,cordic,crc8
intree: Y
vermagic: 3.2.0-3-686-pae SMP mod_unload modversions 686
没有/sys/module/brcmsmac/parameters。这是我在这里的东西：
# tree /sys/module/brcmsmac
/sys/module/brcmsmac
├── drivers
│ └── pci:brcmsmac -> ../../../bus/pci/drivers/brcmsmac
├── holders
├── initstate
├── notes
├── refcnt
├── sections
│ └── __bug_table
└── uevent
有些网站实际可行
正如dr博士所建议，我尝试了其他一些站点，但令我惊讶的是，其中一些确实有效。以下是一些有效的主机：
- rambler.ru
- google.ru
- ya.ru
- opennet.ru
- tut.by
- ro-che.info
- yahoo.com
- ebay.com
这里有一些没有：
- vk.com
- 元
- ukr.net
- tenet.ua
- Prom.ua
- reddit.com
- github.com
- stackexchange.com
网络捕获
我进行了网络捕获并将其上传到此处。
1
出于好奇：发生问题时，NIC的状态是什么？（/ sbin / ifconfig？）
—
yves Baumes
您是否尝试嗅探实际在接口上发送的流量（wireshark / tcpdump ...）？这是什么网卡？无线吗？什么是输出
—
斯特凡Chazelas
iptables-save的，ip rule show，ip route show table all。是否有任何QoS？
用您的问题的答案更新了帖子。
—
Roman Cheplyaka 2012年
我不是从源代码构建驱动程序。该模块本身来自库存的Debian内核（软件包
—
罗曼·切普利卡
linux-image-3.2.0-3-686-pae），而固件来自该firmware-brcm80211软件包。您有与我类似的问题吗？我宁愿避免手工构建东西，除非这是一个已知问题。另外，为什么NIC模块问题会在第4层上显现出来？
Wi-Fi基站，交换机或路由器上很可能出了什么问题。如果可能，请尝试在此处跟踪数据包（或数据包计数）。如果没有，请尝试将其替换为备用项。
—
巴哈马特2012年