adding ethhdr type for linux/android for proper packet filtering. #4239

devnexen · 2025-01-12T11:35:58Z

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rustbot · 2025-01-12T11:36:04Z

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rustbot · 2025-01-12T11:36:07Z

Some changes occurred in the Android module

cc @maurer

maurer

The main thing I see missing here is a use of ethhdr. A struct type with no usage by libc might not actually belong here, even though it is on the UAPI interface - this is a bindings crate for libc, not for the Linux kernel.

Is there a function in libc that you intend to call that uses the ethhdr struct? If so, layering on a commit binding that on top of this one would make a better PR IMO.

maurer · 2025-01-12T17:27:10Z

src/unix/linux_like/android/mod.rs

    }
+
+    // is __be16 __bitwise __u16
+    pub struct __c_anonymous___be16 {


Why __c_anonymous_? This isn't an anonymous type, it's name is __be16.

Unless I'm mistaken, __c_anonymous_fieldname is normally used for inline structs/unions attached to a field of that name - this is a named type, and that's not the field name.

maurer · 2025-01-12T17:28:38Z

src/unix/linux_like/android/mod.rs

+
+        impl Eq for ethhdr {}
+
+        impl PartialEq for ethhdr {


This PartialEq definition appears to lack a check on the h_proto field.

I did not forget but until I solve the alignment issue in some platforms and as I was playing with the h_proto type I do not bother with it just yet (still a draft).

maurer · 2025-01-12T17:29:49Z

src/unix/linux_like/android/mod.rs

+                self.h_dest
+                    .iter()
+                    .zip(other.h_dest.iter())
+                    .all(|(a, b)| a == b)


Do you not want them to compare equal if they have the same CStr value, but different null trailing bytes?

note that those fields represent mac addresses not as strings (note they re unsigned char).

Ah, my bad, you're correct.

maurer · 2025-01-12T17:32:28Z

src/unix/linux_like/android/mod.rs

    }
+
+    // is __be16 __bitwise __u16
+    pub struct __c_anonymous___be16 {


Consider deriving Eq/PartialEq, adding a method to access/set it as host u16, and adding a Debug based on the host representation?

If you do that, your later stuff on ethhdr can just be a derive.

maurer · 2025-01-12T17:33:47Z

src/unix/linux_like/android/mod.rs

+
+    // linux/if_ether.h
+
+    #[repr(C, align(1))]


This struct is packed and not align-1.

I know. was trying to solve few architectures build failures.

maurer · 2025-01-12T17:36:06Z

src/unix/linux_like/android/mod.rs

+                f.debug_struct("ethhdr")
+                    .field("h_dest", &self.h_dest)
+                    .field("h_source", &self.h_source)
+                    .finish()


Missing proto field

maurer · 2025-01-12T17:37:14Z

src/unix/linux_like/linux/mod.rs

    }
+
+    // is __be16 __bitwise __u16
+    pub struct __c_anonymous___be16 {


As above re: __c_anonymous - it also might be helpful just to have a type like this higher up in the hierarchy to be shared, I find the idea that only Linux/Android have bigendian u16s unlikely.

devnexen · 2025-01-12T18:09:42Z

The main thing I see missing here is a use of ethhdr. A struct type with no usage by libc might not actually belong here, even though it is on the UAPI interface - this is a bindings crate for libc, not for the Linux kernel.

There is, for packet filters purpose. sendto/recvfrom can use any buffer e.g. ethhdr for this case. since AF_PACKET family and ETH_P* constants are already there, I m just trying to finish it off.

tgross35 · 2025-02-22T21:00:32Z

Since this is marked as a draft:

@rustbot author

(just update the labels if that isn't accurate)

tgross35 · 2025-04-25T03:50:39Z

This will need a rebase but I think it's ready for review so updating the labels

@rustbot review

tgross35

Sorry this fell off my radar. Just a few requests/questions

libc-test/build.rs

tgross35 · 2025-10-29T22:00:24Z

libc-test/build.rs

+        // FIXME: `h_proto` is of type __be16 big endian version of __u16
+        (struct_ ==  "ethhdr" && field == "h_proto") ||


What doesn't it like here? As far as I can tell, the __be16 type just gets the bitwise attribute which isn't picked up by GCC https://github.com/torvalds/linux/blob/e53642b87a4f4b03a8d7e5f8507fc3cd0c595ea6/include/uapi/linux/types.h#L27-L41.

@devnexen what are the errors with this one?

i forgot since, gonna try removing it

I recall just now it was for some archs only.

src/unix/linux_like/android/mod.rs

rustbot · 2025-10-30T20:55:42Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

devnexen · 2025-10-30T21:25:06Z

@rustbot ready

src/unix/linux_like/android/mod.rs

[ref](https://docs.huihoo.com/doxygen/linux/kernel/3.7/structethhdr.html)

rustbot assigned tgross35 Jan 12, 2025

rustbot added O-android O-linux O-linux-like O-unix S-waiting-on-review labels Jan 12, 2025

devnexen force-pushed the ethhdr_linux branch 5 times, most recently from 55f537d to d478bbb Compare January 12, 2025 12:55

devnexen marked this pull request as draft January 12, 2025 13:00

devnexen force-pushed the ethhdr_linux branch 9 times, most recently from da428da to 4f428e0 Compare January 12, 2025 16:55

maurer reviewed Jan 12, 2025

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devnexen force-pushed the ethhdr_linux branch from 9bb6cb5 to a8ed135 Compare January 12, 2025 20:30

devnexen force-pushed the ethhdr_linux branch 2 times, most recently from 930a40c to 9944b71 Compare January 24, 2025 19:55

rustbot removed the S-waiting-on-review label Feb 22, 2025

rustbot added the S-waiting-on-author label Feb 22, 2025

devnexen force-pushed the ethhdr_linux branch 2 times, most recently from 3c77dba to 7357526 Compare February 22, 2025 21:47

rustbot added the O-gnu label Feb 22, 2025

devnexen marked this pull request as ready for review February 22, 2025 22:21

tgross35 requested a review from maurer April 25, 2025 03:50

rustbot added S-waiting-on-review and removed S-waiting-on-author labels Apr 25, 2025

devnexen force-pushed the ethhdr_linux branch from 7357526 to 1fa2062 Compare April 25, 2025 05:54

tgross35 requested changes Oct 29, 2025

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rustbot added S-waiting-on-author and removed S-waiting-on-review labels Oct 29, 2025

devnexen force-pushed the ethhdr_linux branch from 1fa2062 to f92ae26 Compare October 30, 2025 20:55

devnexen force-pushed the ethhdr_linux branch from f69471d to 0019422 Compare October 30, 2025 21:22

rustbot added S-waiting-on-review and removed S-waiting-on-author labels Oct 30, 2025

tgross35 reviewed Oct 30, 2025

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src/unix/linux_like/android/mod.rs Show resolved Hide resolved

adding ethhdr type for linux/android for proper packet filtering.

94f06b3

[ref](https://docs.huihoo.com/doxygen/linux/kernel/3.7/structethhdr.html)

devnexen force-pushed the ethhdr_linux branch from 6fc575c to 94f06b3 Compare October 30, 2025 22:03

		// FIXME: `h_proto` is of type __be16 big endian version of __u16
		(struct_ == "ethhdr" && field == "h_proto") \|\|

adding ethhdr type for linux/android for proper packet filtering. #4239

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adding ethhdr type for linux/android for proper packet filtering. #4239

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