feat(network): Use ip= parameter for configuring networking by Gelbpunkt · Pull Request #2638 · hermit-os/kernel

Gelbpunkt · 2026-08-13T15:57:03Z

This is a breaking change and replaces HERMIT_IP, HERMIT_MASK, HERMIT_GATEWAY, HERMIT_DNS1 and HERMIT_DNS2 with a single command-line parameter, ip=, which is heavily inspired by Linux.

The kernel will fall back to DHCP if it is enabled, otherwise it will now also no longer fall back to "magic" IPs, instead it will leave the interface unconfigured. Instead, only xtask contains the default static IP configuration that used to reside there and in the kernel.

This is in preparation for adding IPv6 support, which we decided against introducing new variables for. The same mechanism introduced here can be used to support IPv6 with minimal changes.

mkroening · 2026-08-13T16:06:18Z

@jounathaen and @sarahspberrypi are okay with the concept. Is this also ok for you, @stlankes?

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Benchmark Results

Details

Benchmark	Current: `a31d0f6`	Previous: `2e23902`	Performance Ratio
startup_benchmark Build Time	`93.64` s	`80.34` s	`1.17` ❗
startup_benchmark File Size	`0.79` MB	`0.80` MB	`1.00` ❗
Startup Time - 1 core	`0.73` s (`±0.02` s)	`0.75` s (`±0.02` s)	`0.98`
Startup Time - 2 cores	`0.75` s (`±0.02` s)	`0.74` s (`±0.02` s)	`1.02`
Startup Time - 4 cores	`0.74` s (`±0.03` s)	`0.74` s (`±0.02` s)	`1.00`
multithreaded_benchmark Build Time	`91.20` s	`82.11` s	`1.11` ❗
multithreaded_benchmark File Size	`0.85` MB	`0.86` MB	`0.99` ❗
Multithreaded Pi Efficiency - 2 Threads	`88.33` % (`±8.61` %)	`85.89` % (`±6.61` %)	`1.03`
Multithreaded Pi Efficiency - 4 Threads	`43.89` % (`±2.85` %)	`43.43` % (`±2.56` %)	`1.01`
Multithreaded Pi Efficiency - 8 Threads	`25.81` % (`±1.36` %)	`25.76` % (`±1.53` %)	`1.00`
micro_benchmarks Build Time	`94.55` s	`80.40` s	`1.18` ❗
micro_benchmarks File Size	`0.85` MB	`0.86` MB	`0.99` ❗
Scheduling time - 1 thread	`65.02` ticks (`±3.18` ticks)	`62.65` ticks (`±4.06` ticks)	`1.04`
Scheduling time - 2 threads	`36.70` ticks (`±5.23` ticks)	`34.08` ticks (`±4.10` ticks)	`1.08`
Micro - Time for syscall (getpid)	`3.84` ticks (`±0.68` ticks)	`3.45` ticks (`±0.58` ticks)	`1.11`
Memcpy speed - (built_in) block size 4096	`75002.94` MByte/s (`±52303.87` MByte/s)	`82448.38` MByte/s (`±56997.13` MByte/s)	`0.91`
Memcpy speed - (built_in) block size 1048576	`29806.02` MByte/s (`±24065.08` MByte/s)	`30585.98` MByte/s (`±24707.84` MByte/s)	`0.97`
Memcpy speed - (built_in) block size 16777216	`25275.77` MByte/s (`±21053.65` MByte/s)	`26340.06` MByte/s (`±21720.96` MByte/s)	`0.96`
Memset speed - (built_in) block size 4096	`75308.21` MByte/s (`±52474.73` MByte/s)	`82292.76` MByte/s (`±56891.50` MByte/s)	`0.92`
Memset speed - (built_in) block size 1048576	`30521.12` MByte/s (`±24479.60` MByte/s)	`31323.85` MByte/s (`±25145.86` MByte/s)	`0.97`
Memset speed - (built_in) block size 16777216	`26027.22` MByte/s (`±21539.56` MByte/s)	`27104.68` MByte/s (`±22209.94` MByte/s)	`0.96`
Memcpy speed - (rust) block size 4096	`70089.66` MByte/s (`±48829.74` MByte/s)	`74097.96` MByte/s (`±51811.44` MByte/s)	`0.95`
Memcpy speed - (rust) block size 1048576	`29790.64` MByte/s (`±24199.62` MByte/s)	`30361.60` MByte/s (`±24602.37` MByte/s)	`0.98`
Memcpy speed - (rust) block size 16777216	`25762.17` MByte/s (`±21334.69` MByte/s)	`27625.34` MByte/s (`±22806.88` MByte/s)	`0.93`
Memset speed - (rust) block size 4096	`70547.19` MByte/s (`±49114.03` MByte/s)	`74373.47` MByte/s (`±51976.48` MByte/s)	`0.95`
Memset speed - (rust) block size 1048576	`30518.38` MByte/s (`±24610.51` MByte/s)	`31110.89` MByte/s (`±25033.24` MByte/s)	`0.98`
Memset speed - (rust) block size 16777216	`26512.01` MByte/s (`±21807.80` MByte/s)	`28386.93` MByte/s (`±23265.03` MByte/s)	`0.93`
alloc_benchmarks Build Time	`84.28` s	`74.76` s	`1.13` ❗
alloc_benchmarks File Size	`0.87` MB	`0.87` MB	`1.00` ❗
Allocations - Allocation success	`91.38` %	`91.31` %	`1.00` ❗
Allocations - Deallocation success	`100.00` %	`100.00` %	`1`
Allocations - Pre-fail Allocations	`61.60` %	`61.44` %	`1.00` ❗
Allocations - Average Allocation time	`9076.84` Ticks (`±139.95` Ticks)	`5860.58` Ticks (`±98.43` Ticks)	`1.55` ❗
Allocations - Average Allocation time (no fail)	`9652.81` Ticks (`±232.80` Ticks)	`6554.81` Ticks (`±92.86` Ticks)	`1.47` ❗
Allocations - Average Deallocation time	`2711.21` Ticks (`±540.82` Ticks)	`1805.01` Ticks (`±250.35` Ticks)	`1.50` ❗
mutex_benchmark Build Time	`84.81` s	`79.82` s	`1.06` ❗
mutex_benchmark File Size	`0.85` MB	`0.86` MB	`0.99` ❗
Mutex Stress Test Average Time per Iteration - 1 Threads	`12.94` ns (`±0.42` ns)	`12.10` ns (`±0.41` ns)	`1.07` ❗
Mutex Stress Test Average Time per Iteration - 2 Threads	`87.58` ns (`±3.11` ns)	`40.26` ns (`±1.68` ns)	`2.18` ❗

This comment was automatically generated by workflow using github-action-benchmark.

mkroening

Thanks for taking care of this! :)

Does the format also work well with IPv6 addresses? I assume we would do something like ip=[2001:db8::8a2e:370:7334]:[2001:db8::8a2e:370:7334], right?

mkroening · 2026-08-16T11:14:31Z

-				"-ip" => {
-					let ip = expect_arg(words.next(), word.as_str());
-					env_vars.insert(String::from("HERMIT_IP"), ip);
-				}
-				"-mask" => {
-					let mask = expect_arg(words.next(), word.as_str());
-					env_vars.insert(String::from("HERMIT_MASK"), mask);
-				}
-				"-gateway" => {
-					let gateway = expect_arg(words.next(), word.as_str());
-					env_vars.insert(String::from("HERMIT_GATEWAY"), gateway);
-				}


Could you add a warning that these are no longer supported and ip= should be used instead? Same thing for the corresponding hermit_var!(...)s, which are commonly set at compile time at the moment.

Done, wasn't so sure about the warning messages but I hope this is fine

mkroening · 2026-08-16T11:20:23Z

+/// This is heavily inspired by the Linux kernel's parameter of the same name:
+/// <https://docs.kernel.org/admin-guide/nfs/nfsroot.html#kernel-command-line>
+#[derive(Clone, Copy, Debug, Default)]
+pub struct IpConfiguration {


Nit: Move the most important type to the top of the file and the helpers down to help readers with discoverability.

I think I ordered them in a sensible order now, please take a look :)

…MASK Setting just HERMIT_IP=10.0.5.3/24 is much more convenient than HERMIT_IP=10.0.5.3 and HERMIT_MASK=255.255.255.0 and lets us avoid variable hell once we end up adding proper IPv6 support.

This is heavily inspired by Linux' ip= parameter, see https://docs.kernel.org/admin-guide/nfs/nfsroot.html#kernel-command-line The facilities are currently unused and will be replacing HERMIT_IP and HERMIT_GATEWAY in a followup commit.

Gelbpunkt · 2026-08-19T01:48:07Z

Does the format also work well with IPv6 addresses? I assume we would do something like ip=[2001:db8::8a2e:370:7334]:[2001:db8::8a2e:370:7334], right?

Yes, this is roughly what I had in mind. It will work just fine with IPv6 addresses once we do a tiny bit of modifications (since this currently hardcodes IPv4 types, but that's a trivial change later).

I believe dhcp should just imply both dhcpv4 and dhcpv6 eventually if both are available and if we want to use both IPv6 and IPv4 networking on the same interface, we can pass ip= simply twice, once for configuring IPv4 and once for IPv6. Alternatively we could rename dhcp to dhcpv4 and make it explicit.

mkroening

Looks good to me. 👍

Let's wait for @stlankes's opinion in a week. :)

stlankes

I have a few questions...

If I the invalid ip ip=10.0.5.4/64, I got following panic:

[0][PANIC] panicked at /Users/stefan/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/smoltcp-0.14.0/src/wire/ipv4.rs:101:9:
assertion failed: prefix_len <= 32

Also an empty gateway panics. For instance, ip=10.0.5.3/24:: creates following panic.

[0][PANIC] panicked at src/env/mod.rs:86:31:
Could not parse configuration for default interface: invalid gateway IP address

Should we panic on invalid input, or just log a warning?

But I like the PR!

stlankes · 2026-09-13T20:33:19Z

@Gelbpunkt I hope that I fix merge conflicts correctly

stlankes · 2026-09-14T10:22:04Z

I talked to @mkroening and now I am finde with the PR

Gelbpunkt force-pushed the parse-ip-param branch 4 times, most recently from 57eb68d to af2377c Compare August 13, 2026 17:19

mkroening mentioned this pull request Aug 13, 2026

feat(env): remove comptime env vars #2416

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Gelbpunkt force-pushed the parse-ip-param branch from af2377c to 76d38c0 Compare August 13, 2026 18:01

github-actions Bot reviewed Aug 13, 2026

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mkroening self-assigned this Aug 15, 2026

mkroening requested changes Aug 16, 2026

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Gelbpunkt force-pushed the parse-ip-param branch from 76d38c0 to 2c8e3c8 Compare August 18, 2026 22:48

github-actions Bot added ci xtask env executor labels Aug 18, 2026

Gelbpunkt requested a review from mkroening August 18, 2026 22:48

Gelbpunkt added 3 commits August 19, 2026 00:50

refactor(network): Encode prefix length in HERMIT_IP and drop HERMIT_…

c3f0b17

…MASK Setting just HERMIT_IP=10.0.5.3/24 is much more convenient than HERMIT_IP=10.0.5.3 and HERMIT_MASK=255.255.255.0 and lets us avoid variable hell once we end up adding proper IPv6 support.

feat(env): Parse ip= parameter

c2a4301

This is heavily inspired by Linux' ip= parameter, see https://docs.kernel.org/admin-guide/nfs/nfsroot.html#kernel-command-line The facilities are currently unused and will be replacing HERMIT_IP and HERMIT_GATEWAY in a followup commit.

feat(network): Use parsed ip= parameter instead of environment variables

f77d4aa

Gelbpunkt force-pushed the parse-ip-param branch from 2c8e3c8 to f77d4aa Compare August 18, 2026 22:51

mkroening approved these changes Aug 22, 2026

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mkroening assigned stlankes and unassigned mkroening Aug 31, 2026

stlankes and others added 2 commits September 13, 2026 21:40

Merge branch 'main' into parse-ip-param

af07f17

enable nightly feature str_as_str

a31d0f6

stlankes self-requested a review September 13, 2026 20:21

stlankes requested changes Sep 13, 2026

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stlankes approved these changes Sep 14, 2026

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