Add LwIP Ethernet example using tap network driver #494

lschuermann · 2025-02-16T20:30:48Z

This adds an example application running an LwIP-based TCP/IP network
stack and HTTP server based on the EthernetTapDriver kernel capsule,
and the streaming process slice abstractions.

It includes commits from the following other PRs, which I will remove
once they have been merged:

libtock: add util/streaming_process_slice #492: libtock: add util/streaming_process_slice
Configuration.mk: add TOCK_TARGETS for QEMU rv32 virt board #493: Configuration.mk: add TOCK_TARGETS for QEMU rv32 virt board

lschuermann · 2025-02-16T20:55:49Z

@bradjc @ppannuto I couldn't figure out how to exclude the lwip/lwip submodule from the formatting pass. I assume I'm missing something obvious, as it does work for all the other submodules...

Formatting ./lwip_ethernet_tap
../../lwip/Makefile:14: ../../lwip/lwip/src/Filelists.mk: No such file or directory
make: *** No rule to make target '../../lwip/lwip/src/Filelists.mk'.  Stop.
 ⤤ Failure formatting ./lwip_ethernet_tap
Rebuilding Verbose: ./lwip_ethernet_tap

examples/lwip_ethernet_tap/main.c

alistair23 · 2025-02-17T01:04:42Z

examples/lwip_ethernet_tap/main.c

+  *alarm_fired = true;
+}
+
+int main(void) {


Cool!

Can you add a README describing what this does and what is expected?

It would be good to include an example of "it worked on this board at this Tock release"

bradjc · 2025-02-17T16:56:02Z

@lschuermann

libtock-c/u8g2/Makefile

Lines 25 to 26 in 14e590a

    
           # Avoid failing in CI due to warnings in the library. 
        
           override CPPFLAGS_$(LIBNAME) += -Wno-error

bradjc · 2025-02-17T16:59:55Z

Need a https://github.com/tock/libtock-c/blob/master/lvgl/Makefile.setup and can you add a readme to the libtock/util folder to explain what goes in it? I assume we want it to be only be utilities related to abstractions provided by the tock kernel.

This adds userspace helpers implementing the "streaming process slice" contract as implemented in the Tock kernel in [1]. Instead of working with two separate buffers, these helpers present an interface similar to a regular read-write allow based on a single buffer. Internally, this buffer is then subdivided into an "application-owned" and "kernel-owned" part which are swapped atomically. The caller is responsible for keeping a `streaming_process_slice_state_t`, and is provided with ephemeral references to the kernel-written payloads on each swap operation. The full, original buffer can be reclaimed by deinitializing the `streaming_process_slice_state_t` struct. Currently, these helpers are quite minimal and do not expose the ability to set any optional flags (such as `halt`). They are tested to work against against the interface implemented in [1] (with the fix of [2] included) as part of the LwIP Ethernet tap-driver userspace app. [1]: tock/tock#4208 [2]: tock/tock#4343

Instead of internally splitting a single buffer to create two halves used in the streaming process slice abstraction, this changes it to accept two separate buffers for the kernel- and application-owned buffer respectively. This was discussed on the pull request introducing this abstraction: #492 (comment) Suggested-by: Branden Ghena <[email protected]>

lschuermann · 2025-02-21T00:04:24Z

@lschuermann

libtock-c/u8g2/Makefile

Lines 25 to 26 in 14e590a

# Avoid failing in CI due to warnings in the library.

override CPPFLAGS_$(LIBNAME) += -Wno-error

@bradjc Still doesn't fix the formatting errors on the lwip submodule, unfortunately. Any hint on how to disable uncrustify for the submodule?

brghena

Some small things and reminders. But this is just about ready to go once you have time to update it.

brghena · 2025-03-04T04:02:12Z

examples/lwip_ethernet_tap/main.c

+static void frame_rx_upcall(__attribute__((unused)) int   p0,
+                            __attribute__((unused)) int   p1,
+                            __attribute__((unused)) int   p2,
+                            __attribute__((unused)) void* data) {


Copy-paste error: data is actually used in this function

brghena · 2025-03-04T04:03:32Z

examples/lwip_ethernet_tap/main.c

+}
+
+// LwIP packet (Ethernet frame) transmission callback:
+static err_t tapif_output(__attribute__((unused)) struct netif* tapif,


tapif is used in this function

brghena · 2025-03-04T04:07:07Z

examples/lwip_ethernet_tap/main.c

+  *alarm_fired = true;
+}
+
+int main(void) {


It would be good to include an example of "it worked on this board at this Tock release"

brghena · 2025-03-04T04:08:33Z

lwip/Makefile

+# submodule. This is not to be confused with `$(LIBNAME)_DIR` (expands to
+# `lwip_DIR`), which is the top-level Tock directory name:
+LWIPDIR := $($(LIBNAME)_DIR)/$(LIBNAME)/src
+include $($(LIBNAME)_DIR)/lwip/src/Filelists.mk


We discussed on the Network working group call moving this to include a vendored file, as the submodule might not be initialized yet by the time this line runs.

Yeah I think we just copy the makefile and be done with it. Or just copy the lists. It's only ~100 source files.

bradjc · 2025-03-05T21:58:07Z

lwip/Makefile

+override CPPFLAGS += -I$(lwip_DIR)/include -I$(lwip_DIR)/include/lwip
+
+# Avoid failing in CI due to warnings in the library.
+ override CPPFLAGS_$(LIBNAME) += -Wno-error


Suggested change

override CPPFLAGS_$(LIBNAME) += -Wno-error

override CPPFLAGS_$(LIBNAME) += -Wno-error

bradjc · 2025-03-05T22:01:20Z

lwip/Makefile.app

@@ -0,0 +1,3 @@
+include $(TOCK_USERLAND_BASE_DIR)/lwip/Makefile


This shouldn't be here. This makefile should only contain settings to help build an app using this library.

bradjc · 2025-03-05T22:05:09Z

lwip/Makefile

+# submodule. This is not to be confused with `$(LIBNAME)_DIR` (expands to
+# `lwip_DIR`), which is the top-level Tock directory name:
+LWIPDIR := $($(LIBNAME)_DIR)/$(LIBNAME)/src
+include $($(LIBNAME)_DIR)/lwip/src/Filelists.mk


Yeah I think we just copy the makefile and be done with it. Or just copy the lists. It's only ~100 source files.

- Remove unneeded include in Makefile.app - Add necessary Makefile.setup for submodule checkout

ppannuto · 2025-03-06T00:38:08Z

Okay, I believe all the make/build nonsense should be fixed. One thing I'm not 100% sure is okay is 3552552, but I don't really know what else to do here.

I think it's okay because newlib doesn't undef before trying to define BYTE_ORDER, so hopefully if there were ever a conflict due to include ordering, it'd show up as a redefinition warning?

lschuermann force-pushed the dev/lwip-ethernet-tap-example branch from e3e5d40 to 845a712 Compare February 16, 2025 20:43

lschuermann requested review from brghena, alexandruradovici and tyler-potyondy February 16, 2025 20:56

brghena self-assigned this Feb 16, 2025

brghena reviewed Feb 17, 2025

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examples/lwip_ethernet_tap/main.c Outdated Show resolved Hide resolved

alistair23 reviewed Feb 17, 2025

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lschuermann force-pushed the dev/lwip-ethernet-tap-example branch from 487fdd8 to c2bcca3 Compare February 20, 2025 23:58

lschuermann added 2 commits February 20, 2025 19:00

lschuermann force-pushed the dev/lwip-ethernet-tap-example branch from c2bcca3 to 911c62a Compare February 21, 2025 00:03

lschuermann added 2 commits February 20, 2025 19:05

Add LwIP Ethernet example using tap network driver

b939bdc

lwip/lwip: switch from git.savannah.gnu.org to GitHub mirror

55d5027

lschuermann force-pushed the dev/lwip-ethernet-tap-example branch from 911c62a to 55d5027 Compare February 21, 2025 00:05

brghena requested changes Mar 4, 2025

View reviewed changes

bradjc reviewed Mar 5, 2025

View reviewed changes

ppannuto added 4 commits March 5, 2025 15:40

lwip: fix library make rules

deb8651

- Remove unneeded include in Makefile.app - Add necessary Makefile.setup for submodule checkout

lwip: fix include paths and set needed options

bab4e19

lwip: fix include path for app builds

627c467

lwip: resolve conflicting BYTE_ORDER

3552552

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Add LwIP Ethernet example using tap network driver #494

Add LwIP Ethernet example using tap network driver #494

lschuermann commented Feb 16, 2025 •

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ppannuto commented Mar 6, 2025

	override CPPFLAGS_$(LIBNAME) += -Wno-error
	override CPPFLAGS_$(LIBNAME) += -Wno-error

		@@ -0,0 +1,3 @@
		include $(TOCK_USERLAND_BASE_DIR)/lwip/Makefile

Add LwIP Ethernet example using tap network driver #494

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ppannuto commented Mar 6, 2025

lschuermann commented Feb 16, 2025 •

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lschuermann commented Feb 21, 2025 •

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