Running TCP/IP Stack in Linux

Owned by Natalia Sofronova
Last updated: Jun 26, 2024
8 min read

With uClinux running on the i.MX RT1170, you get the full Linux TCP/IP stack (kernel version 4.5.0). Userspace POSIX APIs are provided by the uClibc library. Key user-space networking tools and utilities are available from the multi-call busybox. Additional tools and packages, such as for instance the SSH dropbear server, can be built specifically for uClinux. All in all, you have the powerful Linux TCP/IP stack at your disposal.

There is a full-functioning Ethernet device driver available in the kernel tree for the i.MX RT1170. The device driver is linux/drivers/net/ethernet/freescale/fec.c configured in the kernel using the CONFIG_FEC build time option in Device Drivers -> Network device support -> Ethernet driver support -> Freescale devices -> FEC ethernet controller (of ColdFire and some i.MX CPUs).

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For the run-time configuration of the kernel, Ethernet is enabled in rootfs.dts.IMXRT117X_NXPEVK in projects/rootfs as follows:

&fec1 { pinctrl-names = "default"; pinctrl-0 = <&pinctrl_fec1>, <&pinctrl_fec1_lpsr>; status = "okay"; assigned-clocks = <&clks IMXRT1170_CLK_ROOT_ENET1>; assigned-clock-parents = <&clks IMXRT1170_CLK_PLL1_DIV2>; assigned-clock-rates = <50000000>; fsl,ref-clk-dir = <&gpr 0x10 1 1>; phy-mode = "rmii"; phy-handle = <&ethphy0>; phy-reset-duration = <1>; phy-reset-gpios = <&gpio12 12 GPIO_ACTIVE_LOW>; clocks = <&clks IMXRT1170_CLK_ROOT_BUS>, <&clks IMXRT1170_CLK_ROOT_BUS>, <&clks IMXRT1170_CLK_ENET1>; clock-names = "ipg", "ahb", "enet_clk_ref"; mdio { #address-cells = <1>; #size-cells = <0>; ethphy0: ethernet-phy@0 { reg = <2>; clocks = <&clks IMXRT1170_CLK_ENET1>; clock-names = "rmii-ref"; }; }; };

This will register a platform device for the i.MX RT1170 Ethernet controller with the Ethernet driver.

The Linux project provided by Emcraft in the distribution (refer to projects/rootfs) and installed on each shipping module and kit includes the TCP/IP stack and various network related capabilities. The following snapshot shows the full Linux bootsrap sequence from power-on to the Linux shell:

U-Boot SPL 2023.04 (Sep 01 2023 - 17:34:47 +0000) Trying to boot from MMC1 U-Boot 2023.04 (Sep 01 2023 - 17:34:47 +0000) Model: NXP imxrt1170-evk board DRAM: 960 KiB (effective 64.9 MiB) Core: 72 devices, 15 uclasses, devicetree: separate MMC: FSL_SDHC: 0 Loading Environment from MMC... OK In: serial@4007c000 Out: serial@4007c000 Err: serial@4007c000 Net: eth0: ethernet@40424000 Hit any key to stop autoboot: 0 8489874 bytes read in 756 ms (10.7 MiB/s) ## Booting kernel from Legacy Image at 80007fc0 ... Image Name: Linux-6.1.22 Image Type: ARM Linux Multi-File Image (uncompressed) Data Size: 8489810 Bytes = 8.1 MiB Load Address: 80008000 Entry Point: 80008001 Contents: Image 0: 8480224 Bytes = 8.1 MiB Image 1: 9574 Bytes = 9.3 KiB Verifying Checksum ... OK ## Flattened Device Tree from multi component Image at 80007FC0 Booting using the fdt at 0x8081e5ec Working FDT set to 8081e5ec Loading Multi-File Image Loading Device Tree to 2032a000, end 2032f565 ... OK Working FDT set to 2032a000 Starting kernel ... Booting Linux on physical CPU 0x0 Linux version 6.1.22 (sasha@workbench.emcraft.com) (arm-none-eabi-gcc (GNU Arm Embedded Toolchain 10.3-2021.10) 10.3.1 20210824 (release), GNU ld (GNU Arm Embedded Toolchain 10.3-2021.10) 2.36.1.20210621) #2 Fri Sep 1 14:20:49 UTC 2023 CPU: ARMv7-M [411fc272] revision 2 (ARMv7M), cr=00000000 CPU: PIPT / VIPT nonaliasing data cache, PIPT instruction cache OF: fdt: Machine model: NXP IMXRT1170 EVK board Reserved memory: created DMA memory pool at 0x83f00000, size 1 MiB OF: reserved mem: initialized node dmapool@83f00000, compatible id shared-dma-pool Zone ranges: Normal [mem 0x0000000080000000-0x0000000083ffffff] Movable zone start for each node Early memory node ranges node 0: [mem 0x0000000080000000-0x0000000083efffff] node 0: [mem 0x0000000083f00000-0x0000000083ffffff] Initmem setup node 0 [mem 0x0000000080000000-0x0000000083ffffff] Built 1 zonelists, mobility grouping on. Total pages: 16256 Kernel command line: ip=192.168.88.89:192.168.88.170:192.168.88.1:255. 255.255.0::eth0:off Unknown kernel command line parameters "ip=192.168.88.89:192.168.88.170: 192.168.88.1:255.255.255.0::eth0:off", will be passed to user space. Dentry cache hash table entries: 8192 (order: 3, 32768 bytes, linear) Inode-cache hash table entries: 4096 (order: 2, 16384 bytes, linear) mem auto-init: stack:off, heap alloc:off, heap free:off Memory: 55504K/65536K available (3423K kernel code, 185K rwdata, 908K rodata, 3556K init, 95K bss, 10032K reserved, 0K cma-reserved) NR_IRQS: 16, nr_irqs: 16, preallocated irqs: 16 Switching to timer-based delay loop, resolution 41ns sched_clock: 32 bits at 24MHz, resolution 41ns, wraps every 89478484971ns clocksource: mxc_timer1: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 79635851949 ns Calibrating delay loop (skipped), value calculated using timer frequency.. 48.00 BogoMIPS (lpj=240000) pid_max: default: 4096 minimum: 301 Mount-cache hash table entries: 1024 (order: 0, 4096 bytes, linear) Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes, linear) devtmpfs: initialized DMA: default coherent area is set clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns futex hash table entries: 16 (order: -5, 192 bytes, linear) pinctrl core: initialized pinctrl subsystem NET: Registered PF_NETLINK/PF_ROUTE protocol family imxrt1170-pinctrl 400e8000.iomuxc: initialized IMX pinctrl driver imxrt1170-pinctrl 40c08000.iomuxc_lpsr: initialized IMX pinctrl driver imxrt1170-pinctrl 40c94000.iomuxc_snvs: initialized IMX pinctrl driver SCSI subsystem initialized usbcore: registered new interface driver usbfs usbcore: registered new interface driver hub usbcore: registered new device driver usb pps_core: LinuxPPS API ver. 1 registered pps_core: Software ver. 5.3.6 - Copyright 2005-2007 Rodolfo Giometti <giometti@linux.it> PTP clock support registered Bluetooth: Core ver 2.22 NET: Registered PF_BLUETOOTH protocol family Bluetooth: HCI device and connection manager initialized Bluetooth: HCI socket layer initialized Bluetooth: L2CAP socket layer initialized Bluetooth: SCO socket layer initialized clocksource: Switched to clocksource mxc_timer1 NET: Registered PF_INET protocol family IP idents hash table entries: 2048 (order: 2, 16384 bytes, linear) tcp_listen_portaddr_hash hash table entries: 1024 (order: 0, 4096 bytes, linear) Table-perturb hash table entries: 65536 (order: 6, 262144 bytes, linear) TCP established hash table entries: 1024 (order: 0, 4096 bytes, linear) TCP bind hash table entries: 1024 (order: 1, 8192 bytes, linear) TCP: Hash tables configured (established 1024 bind 1024) UDP hash table entries: 256 (order: 0, 4096 bytes, linear) UDP-Lite hash table entries: 256 (order: 0, 4096 bytes, linear) NET: Registered PF_UNIX/PF_LOCAL protocol family RPC: Registered named UNIX socket transport module. RPC: Registered udp transport module. RPC: Registered tcp transport module. RPC: Registered tcp NFSv4.1 backchannel transport module. Bus freq driver module loaded Initialise system trusted keyrings workingset: timestamp_bits=30 max_order=14 bucket_order=0 fuse: init (API version 7.37) Key type asymmetric registered Asymmetric key parser 'x509' registered Block layer SCSI generic (bsg) driver version 0.4 loaded (major 251) io scheduler mq-deadline registered io scheduler kyber registered 4007c000.serial: ttyLP0 at MMIO 0x4007c010 (irq = 447, base_baud = 1500000) is a FSL_LPUART fsl-lpuart 4007c000.serial: Serial: Console lpuart rounded baud ratefrom 187500 to 115200 printk: console [ttyLP0] enabled PPP generic driver version 2.4.2 PPP BSD Compression module registered PPP Deflate Compression module registered usbcore: registered new interface driver rt2800usb usbcore: registered new interface driver cdc_acm cdc_acm: USB Abstract Control Model driver for USB modems and ISDN adapters usbcore: registered new interface driver uas usbcore: registered new interface driver usb-storage i2c_dev: i2c /dev entries driver usbcore: registered new interface driver btusb sdhci: Secure Digital Host Controller Interface driver sdhci: Copyright(c) Pierre Ossman sdhci-pltfm: SDHCI platform and OF driver helper usbcore: registered new interface driver usbhid usbhid: USB HID core driver NET: Registered PF_PACKET protocol family mmc0 bounce up to 128 segments into one, max segment size 65536 bytes Bluetooth: RFCOMM TTY layer initialized Bluetooth: RFCOMM socket layer initialized Bluetooth: RFCOMM ver 1.11 ARMv7-M VFP coprocessor found VFP: Double precision floating points are supported Loading compiled-in X.509 certificates mmc0: SDHCI controller on 40418000.usdhc [40418000.usdhc] using DMA input: gpio-keys as /devices/platform/gpio-keys/input/input0 cfg80211: Loading compiled-in X.509 certificates for regulatory database cfg80211: Loaded X.509 cert 'sforshee: 00b28ddf47aef9cea7' platform regulatory.0: Direct firmware load for regulatory.db failed with error -2 cfg80211: failed to load regulatory.db Freeing unused kernel image (initmem) memory: 3556K This architecture does not have kernel memory protection. Run /init as init process [72] Jan 01 00:00:01 Running in background / # mmc0: host does not support reading read-only switch, assuming write-enable mmc0: new high speed SDHC card at address 59b4 mmcblk0: mmc0:59b4 USD 7.39 GiB mmcblk0: p1 Micrel KSZ8081 or KSZ8091 40424000.ethernet-1:02: attached PHY driver (mii_bus:phy_addr=40424000.ethernet-1:02, irq=POLL) fec 40424000.ethernet eth0: Link is Up - 100Mbps/Full - flow control off / #

Let's test the TCP/IP stack on the i.MX RT1170.

  1. From the development host validate that the i.MX RT1170 is visible using ping:

    $ ping 192.168.88.89 -c 5 PING 192.168.88.89 (192.168.88.89) 56(84) bytes of data. 64 bytes from 192.168.88.89: icmp_seq=1 ttl=64 time=8.99 ms 64 bytes from 192.168.88.89: icmp_seq=2 ttl=64 time=1.93 ms 64 bytes from 192.168.88.89: icmp_seq=3 ttl=64 time=11.9 ms 64 bytes from 192.168.88.89: icmp_seq=4 ttl=64 time=1.75 ms 64 bytes from 192.168.88.89: icmp_seq=5 ttl=64 time=2.07 ms --- 192.168.88.89 ping statistics --- 5 packets transmitted, 5 received, 0% packet loss, time 405ms rtt min/avg/max/mdev = 1.746/5.323/11.877/4.272 ms

  2. ping the development host from the i.MX RT1170:

  3. On the target, start the telnetd daemon to allow connections to the i.MX RT1170:

  4. Connect to the target from the development host using telnet. The target is configured to accept the 123 password for root.

  5. The dropbear SSH daemon starts automatically on the target. Verify that dropbear allows secure connections to the target:

  6. Connect to the target from the development host using ssh. The first connection takes several seconds to establish as the i.MX RT1170 runs computation-extensive key calculations. Again, enter 123 on the password prompt:

  7. On the target, enable access to the Internet by configuring a default gateway. Note also that the system makes use of the public name server provided by Google:

  8. Use ntpd to synchronize the time on the target with the time provided by a public server:

  9. Use wget to download a file from a remote server:

  10. Mount a directory exported by a development host over NFS:

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