RE(4)

🦋 RE(4) — the RealTek Ethernet adapter driver, bestie edition

okay so like. this is re, from the Kernel Interfaces Manual, and it's genuinely one of the most iconic driver pages ever written. sit down, hydrate, let's go 💖

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✨ NAME ✨

re — RealTek 8139C+/8169/816xS/811xS/8168/810xE/8111 PCI/PCIe Ethernet adapter driver

✨ SYNOPSIS ✨

so if you wanna bake this driver straight into your kernel, bestie, you drop these lines into your kernel configuration file:

device miibus
device re

or — and this is the low-effort slay option — you can load it as a module at boot time by putting this line in loader.conf(5):

if_re_load="YES"

✨ DESCRIPTION ✨

the re driver is out here providing support for a whole girlboss lineup of NICs built on the RealTek RTL8139C+, RTL8169, RTL816xS, RTL811xS, RTL8168, RTL810xE and RTL8111 PCI and PCIe Ethernet controllers. no cap 💅

NICs based on the 8139C+ and 810xE are capable of 10 and 100Mbps speeds over CAT5 cable. NICs based on the 8169, 816xS, 811xS, 8168 and 8111 are capable of 10, 100 and 1000Mbps operation. like, the range? gorgeous.

All NICs supported by the re driver have TCP/IP checksum offload and hardware VLAN tagging/insertion features, and they use a descriptor-based DMA mechanism. they're also capable of TCP large send (TCP segmentation offload). multitasking icon behavior fr fr ✨

now for the lore:

• The 8139C+ is a single-chip solution combining both a 10/100 MAC and PHY.
• The 8169 is a 10/100/1000 MAC only, requiring a GMII or TBI external PHY.
• The 816xS, 811xS, 8168 and 8111 are single-chip devices containing both a 10/100/1000 MAC and 10/100/1000 copper PHY.

Standalone 10/100/1000 cards are available in both 32-bit PCI and 64-bit PCI models. The 8110S is designed for embedded LAN-on-motherboard applications. (motherboard core, honestly.)

The 8169, 8169S and 8110S also support jumbo frames, which can be configured via the interface MTU setting. The MTU is limited to 7422, since the chip cannot transmit larger frames. Selecting an MTU larger than 1500 bytes with the ifconfig(8) utility configures the adapter to receive and transmit jumbo frames. big frames, big feelings 💖

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🌸 media types 🌸

The re driver supports the following media types:

• autoselect — Enable autoselection of the media type and options. The user can manually override the autoselected mode by adding media options to rc.conf(5). it just knows, ok? main character energy.
• 10baseT/UTP — Set 10Mbps operation. The ifconfig(8) mediaopt option can also be used to select either full-duplex or half-duplex modes.
• 100baseTX — Set 100Mbps (Fast Ethernet) operation. The ifconfig(8) mediaopt option can also be used to select either full-duplex or half-duplex modes.
• 1000baseTX — Set 1000baseTX operation over twisted pair. The RealTek gigE chips support 1000Mbps in full-duplex mode only. that's it, that's the only mode, periodt.

🎀 media options 🎀

The re driver supports the following media options:

• full-duplex — Force full duplex operation.
• half-duplex — Force half duplex operation.

For more information on configuring this device, see ifconfig(8). 🫶

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🔥 HARDWARE 🔥

The re driver supports RealTek RTL8139C+, RTL8169, RTL816xS, RTL811xS, RTL8168, RTL810xE and RTL8111 based Fast Ethernet and Gigabit Ethernet adapters including:

• Alloy Computer Products EtherGOLD 1439E 10/100 (8139C+)
• Compaq Evo N1015v Integrated Ethernet (8139C+)
• Corega CG-LAPCIGT Gigabit Ethernet (8169S)
• D-Link DGE-528(T) Gigabit Ethernet (8169S)
• Gigabyte 7N400 Pro2 Integrated Gigabit Ethernet (8110S)
• LevelOne GNC-0105T (8169S)
• LinkSys EG1032 (32-bit PCI)
• PLANEX COMMUNICATIONS Inc. GN-1200TC (8169S)
• TP-Link TG-3468 v2 Gigabit Ethernet (8168)
• USRobotics USR997902 Gigabit Ethernet (8169S)
• Xterasys XN-152 10/100/1000 NIC (8169)

the whole roster ate. 💅✨

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⭐ LOADER TUNABLES ⭐

Tunables can be set at the loader(8) prompt before booting the kernel or stored in loader.conf(5). pick your fighter, bestie.

• hw.re.intr_filter — This tunable makes the driver use the interrupt filter handler on controllers that support MSI/MSI-X capability. If MSI/MSI-X is disabled by the administrator, this tunable has no effect and the driver will use the interrupt filter handler. The default value is 0, to use the interrupt thread handler.
• hw.re.msi_disable — This tunable disables MSI support on the Ethernet hardware. The default value is 0.
• hw.re.msix_disable — This tunable disables MSI-X support on the Ethernet hardware. The default value is 0.
• hw.re.prefer_iomap — This tunable controls which register mapping should be used on the specified device. A non-zero value enables I/O space register mapping. The default value is 0, to use memory space register mapping.

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🌈 SYSCTL VARIABLES 🌈

The following variables are available as both sysctl(8) variables and loader(8) tunables:

• dev.re.%d.int_rx_mod — Maximum amount of time to delay receive interrupt processing, in units of 1us. The accepted range is 0 to 65, the default is 65 (65us). Value 0 completely disables the interrupt moderation. The interface needs to be brought down and up again before a change takes effect.

⚠️ ok so important: that last bit? the interface has to go down and up again before your change does literally anything. no shortcut, sorry bestie 😭

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💀 DIAGNOSTICS 💀

• re%d: couldn't map memory — A fatal initialization error has occurred.
• re%d: couldn't map ports — A fatal initialization error has occurred.
• re%d: couldn't map interrupt — A fatal initialization error has occurred.
• re%d: no memory for softc struct! — The driver failed to allocate memory for per-device instance information during initialization.
• re%d: failed to enable memory mapping! — The driver failed to initialize PCI shared memory mapping. This might happen if the card is not in a bus-master slot.
• re%d: no memory for jumbo buffers! — The driver failed to allocate memory for jumbo frames during initialization.
• re%d: watchdog timeout — The device has stopped responding to the network, or there is a problem with the network connection (cable).

if you see one of these, that's not a vibe, that's a cry for help 🙈

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🧚 SEE ALSO 🧚

altq(4), arp(4), miibus(4), netintro(4), ng_ether(4), polling(4), rgephy(4), vlan(4), ifconfig(8)

RealTek Semiconductor RTL8139C+, RTL8169, RTL8169S and RTL8110S datasheets, http://www.realtek.com.tw/.

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🎀 HISTORY 🎀

The re device driver first appeared in FreeBSD 5.2. an icon from day one, honestly.

👑 AUTHORS 👑

The re driver was written by Bill Paul <wpaul@windriver.com>. king behavior 💜

😭 BUGS 😭

ok bestie, this part is serious, so listen up.

The Xterasys XN-152 32-bit PCI NIC, which uses the RTL8169 MAC and Marvell 88E1000 PHY, has a defect that causes DMA corruption if the board is plugged into a 64-bit PCI slot. The defect lies in the board design, not the chip itself: the PCI REQ64# and ACK64# lines should be pulled high, but they are not. The result is that the 8169 chip is tricked into performing 64-bit DMA transfers even though a 64-bit data path between the NIC and the bus does not actually exist. not the chip's fault, the board really said "we're not doing that" and then did it anyway 💀

Unfortunately, it is not possible to correct this problem in software, however it is possible to detect it. When the re driver is loaded, it will run a diagnostic routine designed to validate DMA operation by placing the chip in digital loopback mode and initiating a packet transmission. If the card functions properly, the transmitted data will be echoed back unmodified. If the echoed data is corrupt, the driver will print an error message on the console and abort the device attach.

🚨 The user should ensure the NIC is installed in a 32-bit PCI slot to avoid this problem. fr fr, do this.

The RealTek 8169, 8169S and 8110S chips appear to only be capable of transmitting jumbo frames up to 7.5K in size.

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and that's the whole page, bestie 🫶 this one came from the Debian fam, dated September 21, 2016, and it's filed as RE(4) in the Kernel Interfaces Manual. go forth and network responsibly 💖✨🌸