Testing a small http-client on Linux using no_std & embedded reqwless.
implement default posix backend and dns mode feature model
+152
-3
+51
Cargo.lock
+51
Cargo.lock
···
62
62
checksum = "9d297deb1925b89f2ccc13d7635fa0714f12c87adce1c75356b39ca9b7178567"
63
63
64
64
[[package]]
65
+
name = "bitflags"
66
+
version = "2.11.0"
67
+
source = "registry+https://github.com/rust-lang/crates.io-index"
68
+
checksum = "843867be96c8daad0d758b57df9392b6d8d271134fce549de6ce169ff98a92af"
69
+
70
+
[[package]]
65
71
name = "block-buffer"
66
72
version = "0.10.4"
67
73
source = "registry+https://github.com/rust-lang/crates.io-index"
···
350
356
]
351
357
352
358
[[package]]
359
+
name = "errno"
360
+
version = "0.3.14"
361
+
source = "registry+https://github.com/rust-lang/crates.io-index"
362
+
checksum = "39cab71617ae0d63f51a36d69f866391735b51691dbda63cf6f96d042b63efeb"
363
+
dependencies = [
364
+
"libc",
365
+
"windows-sys",
366
+
]
367
+
368
+
[[package]]
353
369
name = "ff"
354
370
version = "0.13.1"
355
371
source = "registry+https://github.com/rust-lang/crates.io-index"
···
501
517
checksum = "b5b646652bf6661599e1da8901b3b9522896f01e736bad5f723fe7a3a27f899d"
502
518
503
519
[[package]]
520
+
name = "linux-raw-sys"
521
+
version = "0.12.1"
522
+
source = "registry+https://github.com/rust-lang/crates.io-index"
523
+
checksum = "32a66949e030da00e8c7d4434b251670a91556f4144941d37452769c25d58a53"
524
+
525
+
[[package]]
504
526
name = "nb"
505
527
version = "1.1.0"
506
528
source = "registry+https://github.com/rust-lang/crates.io-index"
···
666
688
"embedded-nal-async",
667
689
"libc",
668
690
"reqwless",
691
+
"rustix",
669
692
]
670
693
671
694
[[package]]
···
688
711
]
689
712
690
713
[[package]]
714
+
name = "rustix"
715
+
version = "1.1.4"
716
+
source = "registry+https://github.com/rust-lang/crates.io-index"
717
+
checksum = "b6fe4565b9518b83ef4f91bb47ce29620ca828bd32cb7e408f0062e9930ba190"
718
+
dependencies = [
719
+
"bitflags",
720
+
"errno",
721
+
"libc",
722
+
"linux-raw-sys",
723
+
"windows-sys",
724
+
]
725
+
726
+
[[package]]
691
727
name = "sec1"
692
728
version = "0.7.3"
693
729
source = "registry+https://github.com/rust-lang/crates.io-index"
···
804
840
version = "0.9.5"
805
841
source = "registry+https://github.com/rust-lang/crates.io-index"
806
842
checksum = "0b928f33d975fc6ad9f86c8f283853ad26bdd5b10b7f1542aa2fa15e2289105a"
843
+
844
+
[[package]]
845
+
name = "windows-link"
846
+
version = "0.2.1"
847
+
source = "registry+https://github.com/rust-lang/crates.io-index"
848
+
checksum = "f0805222e57f7521d6a62e36fa9163bc891acd422f971defe97d64e70d0a4fe5"
849
+
850
+
[[package]]
851
+
name = "windows-sys"
852
+
version = "0.61.2"
853
+
source = "registry+https://github.com/rust-lang/crates.io-index"
854
+
checksum = "ae137229bcbd6cdf0f7b80a31df61766145077ddf49416a728b02cb3921ff3fc"
855
+
dependencies = [
856
+
"windows-link",
857
+
]
807
858
808
859
[[package]]
809
860
name = "zerocopy"
+6
-1
Cargo.toml
+6
-1
Cargo.toml
···
4
4
edition = "2024"
5
5
6
6
[features]
7
-
default = []
7
+
default = ["backend-posix-libc", "dns-getaddrinfo"]
8
+
backend-posix-libc = []
9
+
backend-rustix = ["dep:rustix"]
10
+
dns-getaddrinfo = []
11
+
dns-ip-only = []
8
12
https = ["reqwless/embedded-tls", "dep:der"]
9
13
10
14
[dependencies]
···
14
18
der = { version = "0.8", default-features = false, features = ["derive", "oid", "time", "heapless"], optional = true }
15
19
libc = { version = "0.2", default-features = false }
16
20
reqwless = { version = "0.14", default-features = false }
21
+
rustix = { version = "1.1", default-features = false, features = ["net"], optional = true }
17
22
18
23
[profile.dev]
19
24
panic = "abort"
+16
README.md
+16
README.md
···
20
20
21
21
- `no_std` + `no_main` binary using Linux libc syscalls
22
22
- Uses `reqwless` with `default-features = false`
23
+
- Default feature set is `backend-posix-libc` + `dns-getaddrinfo`
24
+
- Planned `backend-rustix` exists as a feature gate but is intentionally not implemented yet
25
+
- Alternate DNS mode `dns-ip-only` rejects hostnames and only accepts literal IP hosts
23
26
- HTTPS is optional via `--features https` and currently uses `TlsVerify::None` (insecure baseline)
24
27
- Uses fixed-size stack buffers for request/response and output chunks
25
28
- Performs best-effort low-allocation operation (no `String`/`Vec` in app code)
29
+
30
+
## Feature examples
31
+
32
+
```bash
33
+
# Default build: posix-libc backend + getaddrinfo DNS mode
34
+
cargo run -- http://example.com
35
+
36
+
# HTTPS on default backend/DNS mode
37
+
cargo run --features https -- https://example.com
38
+
39
+
# Minimal DNS mode (literal IP hosts only)
40
+
cargo run --no-default-features --features backend-posix-libc,dns-ip-only -- http://93.184.216.34
41
+
```
+79
-2
src/main.rs
+79
-2
src/main.rs
···
3
3
4
4
// pattern: Imperative Shell
5
5
6
+
#[cfg(all(feature = "backend-posix-libc", feature = "backend-rustix"))]
7
+
compile_error!("enable exactly one backend: backend-posix-libc or backend-rustix");
8
+
9
+
#[cfg(not(any(feature = "backend-posix-libc", feature = "backend-rustix")))]
10
+
compile_error!("no backend selected; enable backend-posix-libc or backend-rustix");
11
+
12
+
#[cfg(all(feature = "dns-getaddrinfo", feature = "dns-ip-only"))]
13
+
compile_error!("enable exactly one DNS mode: dns-getaddrinfo or dns-ip-only");
14
+
15
+
#[cfg(not(any(feature = "dns-getaddrinfo", feature = "dns-ip-only")))]
16
+
compile_error!("no DNS mode selected; enable dns-getaddrinfo or dns-ip-only");
17
+
18
+
#[cfg(feature = "backend-rustix")]
19
+
compile_error!("backend-rustix is not implemented yet; use backend-posix-libc");
20
+
6
21
use core::ffi::{CStr, c_char, c_int, c_void};
7
22
use core::future::Future;
8
-
use core::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr};
23
+
use core::net::{IpAddr, SocketAddr};
24
+
#[cfg(feature = "dns-getaddrinfo")]
25
+
use core::net::{Ipv4Addr, Ipv6Addr};
9
26
use core::panic::PanicInfo;
10
27
use core::pin::Pin;
11
28
use core::ptr;
···
24
41
const EXIT_USAGE: c_int = 2;
25
42
const EXIT_FAILURE: c_int = 1;
26
43
44
+
#[cfg(feature = "dns-getaddrinfo")]
27
45
const DNS_HOST_MAX: usize = 255;
28
46
#[cfg(feature = "https")]
29
47
const TLS_BUFFER_SIZE: usize = 16 * 1024;
···
43
61
MissingUrl,
44
62
#[cfg(not(feature = "https"))]
45
63
HttpsFeatureDisabled,
64
+
#[cfg(feature = "dns-ip-only")]
65
+
DnsModeIpOnly,
46
66
InvalidUtf8,
67
+
#[cfg(feature = "dns-getaddrinfo")]
47
68
UrlTooLong,
69
+
#[cfg(feature = "dns-getaddrinfo")]
48
70
NulInHost,
49
71
DnsLookupFailed,
50
72
AddrTypeMismatch,
···
58
80
Self::MissingUrl => ErrorKind::InvalidInput,
59
81
#[cfg(not(feature = "https"))]
60
82
Self::HttpsFeatureDisabled => ErrorKind::Unsupported,
83
+
#[cfg(feature = "dns-ip-only")]
84
+
Self::DnsModeIpOnly => ErrorKind::Unsupported,
61
85
Self::InvalidUtf8 => ErrorKind::InvalidData,
86
+
#[cfg(feature = "dns-getaddrinfo")]
62
87
Self::UrlTooLong => ErrorKind::InvalidInput,
88
+
#[cfg(feature = "dns-getaddrinfo")]
63
89
Self::NulInHost => ErrorKind::InvalidInput,
64
90
Self::DnsLookupFailed => ErrorKind::NotFound,
65
91
Self::AddrTypeMismatch => ErrorKind::AddrNotAvailable,
···
89
115
Self::MissingUrl => "missing url argument",
90
116
#[cfg(not(feature = "https"))]
91
117
Self::HttpsFeatureDisabled => "https support not enabled",
118
+
#[cfg(feature = "dns-ip-only")]
119
+
Self::DnsModeIpOnly => "dns mode only accepts ip literals",
92
120
Self::InvalidUtf8 => "url argument must be valid utf-8",
121
+
#[cfg(feature = "dns-getaddrinfo")]
93
122
Self::UrlTooLong => "hostname is too long",
123
+
#[cfg(feature = "dns-getaddrinfo")]
94
124
Self::NulInHost => "hostname contains NUL byte",
95
125
Self::DnsLookupFailed => "dns lookup failed",
96
126
Self::AddrTypeMismatch => "address type mismatch",
···
188
218
return Err(AppError::AddrTypeMismatch);
189
219
}
190
220
191
-
resolve_host(host, addr_type)
221
+
#[cfg(feature = "dns-getaddrinfo")]
222
+
{
223
+
return resolve_host(host, addr_type);
224
+
}
225
+
226
+
#[cfg(feature = "dns-ip-only")]
227
+
{
228
+
let _ = host;
229
+
let _ = addr_type;
230
+
Err(AppError::DnsModeIpOnly)
231
+
}
192
232
}
193
233
194
234
async fn get_host_by_address(&self, _addr: IpAddr, _result: &mut [u8]) -> Result<usize, Self::Error> {
···
220
260
}
221
261
222
262
async fn download_to_stdout(url: &str) -> Result<(), AppError> {
263
+
#[cfg(feature = "dns-ip-only")]
264
+
ensure_url_uses_ip_literal_host(url)?;
265
+
223
266
if url.starts_with("https://") {
224
267
return download_https_to_stdout(url).await;
225
268
}
···
272
315
Ok(())
273
316
}
274
317
318
+
#[cfg(feature = "dns-ip-only")]
319
+
fn ensure_url_uses_ip_literal_host(url: &str) -> Result<(), AppError> {
320
+
let after_scheme = if let Some(rest) = url.strip_prefix("http://") {
321
+
rest
322
+
} else if let Some(rest) = url.strip_prefix("https://") {
323
+
rest
324
+
} else {
325
+
return Ok(());
326
+
};
327
+
328
+
let authority = after_scheme.split_once('/').map_or(after_scheme, |(prefix, _)| prefix);
329
+
let authority = authority.split_once('?').map_or(authority, |(prefix, _)| prefix);
330
+
let authority = authority.split_once('#').map_or(authority, |(prefix, _)| prefix);
331
+
332
+
let host_port = authority.rsplit_once('@').map_or(authority, |(_, hp)| hp);
333
+
let host = if host_port.starts_with('[') {
334
+
let end = host_port.find(']').ok_or(AppError::DnsModeIpOnly)?;
335
+
&host_port[1..end]
336
+
} else {
337
+
host_port.split_once(':').map_or(host_port, |(h, _)| h)
338
+
};
339
+
340
+
if host.parse::<IpAddr>().is_err() {
341
+
return Err(AppError::DnsModeIpOnly);
342
+
}
343
+
344
+
Ok(())
345
+
}
346
+
275
347
fn print_usage() {
276
348
#[cfg(feature = "https")]
277
349
write_stderr(b"usage: reqwless-linux <http://url|https://url>\n");
···
294
366
cstr.to_str().map_err(|_| AppError::InvalidUtf8)
295
367
}
296
368
369
+
#[cfg(feature = "dns-getaddrinfo")]
297
370
fn resolve_host(host: &str, addr_type: AddrType) -> Result<IpAddr, AppError> {
298
371
if host.len() > DNS_HOST_MAX {
299
372
return Err(AppError::UrlTooLong);
···
443
516
AppError::MissingUrl => write_stderr(b"missing url argument\n"),
444
517
#[cfg(not(feature = "https"))]
445
518
AppError::HttpsFeatureDisabled => write_stderr(b"https url requires --features https\n"),
519
+
#[cfg(feature = "dns-ip-only")]
520
+
AppError::DnsModeIpOnly => write_stderr(b"dns-ip-only mode accepts literal IP hosts only\n"),
446
521
AppError::InvalidUtf8 => write_stderr(b"url argument must be valid utf-8\n"),
522
+
#[cfg(feature = "dns-getaddrinfo")]
447
523
AppError::UrlTooLong => write_stderr(b"hostname is too long\n"),
524
+
#[cfg(feature = "dns-getaddrinfo")]
448
525
AppError::NulInHost => write_stderr(b"hostname contains NUL byte\n"),
449
526
AppError::DnsLookupFailed => write_stderr(b"dns lookup failed\n"),
450
527
AppError::AddrTypeMismatch => write_stderr(b"address type mismatch\n"),