Created attachment 198851 [details]
networkmanager log

If I try to establish a wired connection on my Notebook via DHCP (only DHCP is affected, not manual configuration), it will take several attempts and time (see networkmanager log) before it finally works. Thereby it doesn't matter if I use the networkmanager or plain dhcp with dhclient or dhcpcd. Straight before the DHCP connection will be established the kernel prints that message:
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Jan 06 16:34:49 ultrabook kernel: ------------[ cut here ]------------
Jan 06 16:34:49 ultrabook kernel: WARNING: CPU: 2 PID: 0 at net/sched/sch_generic.c:303 dev_watchdog+0x217/0x220()
Jan 06 16:34:49 ultrabook kernel: NETDEV WATCHDOG: enp3s0f1 (r8169): transmit queue 0 timed out
Jan 06 16:34:49 ultrabook kernel: Modules linked in: tpm_infineon iwlmvm rtsx_pci_sdmmc snd_hda_codec_realtek snd_hda_codec_generic snd_hda_codec_hdmi iwlwifi rtsx_pci snd_hda_intel r8169 snd_hda_codec mfd_core snd_hwdep snd_hda_core tpm_tis sdhci_acpi sdhci efivarfs
Jan 06 16:34:49 ultrabook kernel: CPU: 2 PID: 0 Comm: swapper/2 Tainted: G          I     4.3.3 #2
Jan 06 16:34:49 ultrabook kernel: Hardware name: Notebook                         W840SU Series                    /W840SU Series                    , BIOS 4.6.5 11/21/2013
Jan 06 16:34:49 ultrabook kernel:  ffffffff99c29827 ffff88021fb03df8 ffffffff992f74cf ffff88021fb03e40
Jan 06 16:34:49 ultrabook kernel:  ffff88021fb03e30 ffffffff9907bf2c 0000000000000000 ffff8800d9340000
Jan 06 16:34:49 ultrabook kernel:  0000000000000002 0000000000000001 ffff88021fb0ca00 ffff88021fb03e90
Jan 06 16:34:49 ultrabook kernel: Call Trace:
Jan 06 16:34:49 ultrabook kernel:  <IRQ>  [<ffffffff992f74cf>] dump_stack+0x44/0x55
Jan 06 16:34:49 ultrabook kernel:  [<ffffffff9907bf2c>] warn_slowpath_common+0x7c/0xb0
Jan 06 16:34:49 ultrabook kernel:  [<ffffffff9907bfa7>] warn_slowpath_fmt+0x47/0x50
Jan 06 16:34:49 ultrabook kernel:  [<ffffffff99665257>] dev_watchdog+0x217/0x220
Jan 06 16:34:49 ultrabook kernel:  [<ffffffff99665040>] ? dev_graft_qdisc+0x70/0x70
Jan 06 16:34:49 ultrabook kernel:  [<ffffffff990c7d97>] call_timer_fn.isra.27+0x17/0x70
Jan 06 16:34:49 ultrabook kernel:  [<ffffffff990c7f0e>] run_timer_softirq+0x11e/0x1e0
Jan 06 16:34:49 ultrabook kernel:  [<ffffffff9907f84c>] __do_softirq+0xdc/0x1d0
Jan 06 16:34:49 ultrabook kernel:  [<ffffffff9907fa50>] irq_exit+0x70/0x90
Jan 06 16:34:49 ultrabook kernel:  [<ffffffff990332bd>] smp_apic_timer_interrupt+0x3d/0x50
Jan 06 16:34:49 ultrabook kernel:  [<ffffffff997fd24f>] apic_timer_interrupt+0x7f/0x90
Jan 06 16:34:49 ultrabook kernel:  <EOI>  [<ffffffff995bb758>] ? cpuidle_enter_state+0x108/0x1b0
Jan 06 16:34:49 ultrabook kernel:  [<ffffffff995bb822>] cpuidle_enter+0x12/0x20
Jan 06 16:34:49 ultrabook kernel:  [<ffffffff990afd7d>] call_cpuidle+0x2d/0x50
Jan 06 16:34:49 ultrabook kernel:  [<ffffffff995bb80e>] ? cpuidle_select+0xe/0x10
Jan 06 16:34:49 ultrabook kernel:  [<ffffffff990aff5b>] cpu_startup_entry+0x1bb/0x260
Jan 06 16:34:49 ultrabook kernel:  [<ffffffff9903175c>] start_secondary+0x12c/0x140
Jan 06 16:34:49 ultrabook kernel: ---[ end trace 35f5116148e81cf0 ]---
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lspci -v about my network card:
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03:00.1 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 12)
	Subsystem: CLEVO/KAPOK Computer RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
	Flags: bus master, fast devsel, latency 0, IRQ 43
	I/O ports at e000 [size=256]
	Memory at f7c14000 (64-bit, non-prefetchable) [size=4K]
	Memory at f7c10000 (64-bit, non-prefetchable) [size=16K]
	Capabilities: [40] Power Management version 3
	Capabilities: [50] MSI: Enable+ Count=1/1 Maskable- 64bit+
	Capabilities: [70] Express Endpoint, MSI 01
	Capabilities: [b0] MSI-X: Enable- Count=4 Masked-
	Capabilities: [d0] Vital Product Data
	Capabilities: [100] Advanced Error Reporting
	Capabilities: [160] Device Serial Number 01-00-00-00-68-4c-e0-00
	Capabilities: [170] Latency Tolerance Reporting
	Capabilities: [178] L1 PM Substates
	Kernel driver in use: r8169
	Kernel modules: r8169
------------------------------------------------------------------------------

Do you have an idea how I can debug the r8169 kernel module? I've been looking via google but it said that I'd need a "JTAG" interface which I don't have. My notebook doesn't have a serial port either.