Implement rollback and reboot

This is a copy of the logic from rustkrazy_admind (to prevent a high
amount of dependencies for an HTTPS client). Signals cannot be used
without losing the ability to handle errors.

3 files changed, 457 insertions, 3 deletions

diff --git a/Cargo.lock b/Cargo.lock
index e007574..b45e9a2 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1,7 +1,376 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 3
+version = 4
+
+[[package]]
+name = "android-tzdata"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e999941b234f3131b00bc13c22d06e8c5ff726d1b6318ac7eb276997bbb4fef0"
+
+[[package]]
+name = "android_system_properties"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "819e7219dbd41043ac279b19830f2efc897156490d7fd6ea916720117ee66311"
+dependencies = [
+ "libc",
+]
+
+[[package]]
+name = "autocfg"
+version = "1.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ace50bade8e6234aa140d9a2f552bbee1db4d353f69b8217bc503490fc1a9f26"
+
+[[package]]
+name = "bitflags"
+version = "1.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
+
+[[package]]
+name = "bitflags"
+version = "2.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5c8214115b7bf84099f1309324e63141d4c5d7cc26862f97a0a857dbefe165bd"
+
+[[package]]
+name = "bumpalo"
+version = "3.17.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1628fb46dfa0b37568d12e5edd512553eccf6a22a78e8bde00bb4aed84d5bdbf"
+
+[[package]]
+name = "byteorder"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1fd0f2584146f6f2ef48085050886acf353beff7305ebd1ae69500e27c67f64b"
+
+[[package]]
+name = "cc"
+version = "1.2.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1fcb57c740ae1daf453ae85f16e37396f672b039e00d9d866e07ddb24e328e3a"
+dependencies = [
+ "shlex",
+]
+
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
+[[package]]
+name = "cfg_aliases"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "613afe47fcd5fac7ccf1db93babcb082c5994d996f20b8b159f2ad1658eb5724"
+
+[[package]]
+name = "chrono"
+version = "0.4.40"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1a7964611d71df112cb1730f2ee67324fcf4d0fc6606acbbe9bfe06df124637c"
+dependencies = [
+ "android-tzdata",
+ "iana-time-zone",
+ "js-sys",
+ "num-traits",
+ "wasm-bindgen",
+ "windows-link",
+]
+
+[[package]]
+name = "core-foundation-sys"
+version = "0.8.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "773648b94d0e5d620f64f280777445740e61fe701025087ec8b57f45c791888b"
+
+[[package]]
+name = "fatfs"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "05669f8e7e2d7badc545c513710f0eba09c2fbef683eb859fd79c46c355048e0"
+dependencies = [
+ "bitflags 1.3.2",
+ "byteorder",
+ "chrono",
+ "log",
+]
+
+[[package]]
+name = "fscommon"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "315ce685aca5ddcc5a3e7e436ef47d4a5d0064462849b6f0f628c28140103531"
+dependencies = [
+ "log",
+]
+
+[[package]]
+name = "iana-time-zone"
+version = "0.1.62"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b2fd658b06e56721792c5df4475705b6cda790e9298d19d2f8af083457bcd127"
+dependencies = [
+ "android_system_properties",
+ "core-foundation-sys",
+ "iana-time-zone-haiku",
+ "js-sys",
+ "log",
+ "wasm-bindgen",
+ "windows-core",
+]
+
+[[package]]
+name = "iana-time-zone-haiku"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f31827a206f56af32e590ba56d5d2d085f558508192593743f16b2306495269f"
+dependencies = [
+ "cc",
+]
+
+[[package]]
+name = "js-sys"
+version = "0.3.77"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1cfaf33c695fc6e08064efbc1f72ec937429614f25eef83af942d0e227c3a28f"
+dependencies = [
+ "once_cell",
+ "wasm-bindgen",
+]
+
+[[package]]
+name = "libc"
+version = "0.2.171"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c19937216e9d3aa9956d9bb8dfc0b0c8beb6058fc4f7a4dc4d850edf86a237d6"
+
+[[package]]
+name = "log"
+version = "0.4.27"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "13dc2df351e3202783a1fe0d44375f7295ffb4049267b0f3018346dc122a1d94"
+
+[[package]]
+name = "nix"
+version = "0.29.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "71e2746dc3a24dd78b3cfcb7be93368c6de9963d30f43a6a73998a9cf4b17b46"
+dependencies = [
+ "bitflags 2.9.0",
+ "cfg-if",
+ "cfg_aliases",
+ "libc",
+]
+
+[[package]]
+name = "num-traits"
+version = "0.2.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "071dfc062690e90b734c0b2273ce72ad0ffa95f0c74596bc250dcfd960262841"
+dependencies = [
+ "autocfg",
+]
+
+[[package]]
+name = "once_cell"
+version = "1.21.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d75b0bedcc4fe52caa0e03d9f1151a323e4aa5e2d78ba3580400cd3c9e2bc4bc"
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.94"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a31971752e70b8b2686d7e46ec17fb38dad4051d94024c88df49b667caea9c84"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.40"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1885c039570dc00dcb4ff087a89e185fd56bae234ddc7f056a945bf36467248d"
+dependencies = [
+ "proc-macro2",
+]
 
 [[package]]
 name = "rsdsl_diagd"
 version = "0.1.0"
+dependencies = [
+ "fatfs",
+ "fscommon",
+ "nix",
+]
+
+[[package]]
+name = "rustversion"
+version = "1.0.20"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eded382c5f5f786b989652c49544c4877d9f015cc22e145a5ea8ea66c2921cd2"
+
+[[package]]
+name = "shlex"
+version = "1.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0fda2ff0d084019ba4d7c6f371c95d8fd75ce3524c3cb8fb653a3023f6323e64"
+
+[[package]]
+name = "syn"
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b09a44accad81e1ba1cd74a32461ba89dee89095ba17b32f5d03683b1b1fc2a0"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a5f39404a5da50712a4c1eecf25e90dd62b613502b7e925fd4e4d19b5c96512"
+
+[[package]]
+name = "wasm-bindgen"
+version = "0.2.100"
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+checksum = "1edc8929d7499fc4e8f0be2262a241556cfc54a0bea223790e71446f2aab1ef5"
+dependencies = [
+ "cfg-if",
+ "once_cell",
+ "rustversion",
+ "wasm-bindgen-macro",
+]
+
+[[package]]
+name = "wasm-bindgen-backend"
+version = "0.2.100"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2f0a0651a5c2bc21487bde11ee802ccaf4c51935d0d3d42a6101f98161700bc6"
+dependencies = [
+ "bumpalo",
+ "log",
+ "proc-macro2",
+ "quote",
+ "syn",
+ "wasm-bindgen-shared",
+]
+
+[[package]]
+name = "wasm-bindgen-macro"
+version = "0.2.100"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7fe63fc6d09ed3792bd0897b314f53de8e16568c2b3f7982f468c0bf9bd0b407"
+dependencies = [
+ "quote",
+ "wasm-bindgen-macro-support",
+]
+
+[[package]]
+name = "wasm-bindgen-macro-support"
+version = "0.2.100"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8ae87ea40c9f689fc23f209965b6fb8a99ad69aeeb0231408be24920604395de"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+ "wasm-bindgen-backend",
+ "wasm-bindgen-shared",
+]
+
+[[package]]
+name = "wasm-bindgen-shared"
+version = "0.2.100"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1a05d73b933a847d6cccdda8f838a22ff101ad9bf93e33684f39c1f5f0eece3d"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "windows-core"
+version = "0.52.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "33ab640c8d7e35bf8ba19b884ba838ceb4fba93a4e8c65a9059d08afcfc683d9"
+dependencies = [
+ "windows-targets",
+]
+
+[[package]]
+name = "windows-link"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "76840935b766e1b0a05c0066835fb9ec80071d4c09a16f6bd5f7e655e3c14c38"
+
+[[package]]
+name = "windows-targets"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9b724f72796e036ab90c1021d4780d4d3d648aca59e491e6b98e725b84e99973"
+dependencies = [
+ "windows_aarch64_gnullvm",
+ "windows_aarch64_msvc",
+ "windows_i686_gnu",
+ "windows_i686_gnullvm",
+ "windows_i686_msvc",
+ "windows_x86_64_gnu",
+ "windows_x86_64_gnullvm",
+ "windows_x86_64_msvc",
+]
+
+[[package]]
+name = "windows_aarch64_gnullvm"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "32a4622180e7a0ec044bb555404c800bc9fd9ec262ec147edd5989ccd0c02cd3"
+
+[[package]]
+name = "windows_aarch64_msvc"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "09ec2a7bb152e2252b53fa7803150007879548bc709c039df7627cabbd05d469"
+
+[[package]]
+name = "windows_i686_gnu"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8e9b5ad5ab802e97eb8e295ac6720e509ee4c243f69d781394014ebfe8bbfa0b"
+
+[[package]]
+name = "windows_i686_gnullvm"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0eee52d38c090b3caa76c563b86c3a4bd71ef1a819287c19d586d7334ae8ed66"
+
+[[package]]
+name = "windows_i686_msvc"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "240948bc05c5e7c6dabba28bf89d89ffce3e303022809e73deaefe4f6ec56c66"
+
+[[package]]
+name = "windows_x86_64_gnu"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "147a5c80aabfbf0c7d901cb5895d1de30ef2907eb21fbbab29ca94c5b08b1a78"
+
+[[package]]
+name = "windows_x86_64_gnullvm"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "24d5b23dc417412679681396f2b49f3de8c1473deb516bd34410872eff51ed0d"
+
+[[package]]
+name = "windows_x86_64_msvc"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "589f6da84c646204747d1270a2a5661ea66ed1cced2631d546fdfb155959f9ec"
diff --git a/Cargo.toml b/Cargo.toml
index cf5a7ca..698c492 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,3 +6,6 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+fatfs = "0.3.6"
+fscommon = "0.1.1"
+nix = { version = "0.29.0", default-features = false, features = ["fs", "signal"] }
diff --git a/src/main.rs b/src/main.rs
index f08e8a6..ebe921f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -23,6 +23,9 @@ use std::io::{self, Read, Write};
 use std::net::{Shutdown, SocketAddr, TcpListener, TcpStream};
 use std::time::{Duration, Instant};
 
+use nix::sys::signal::Signal;
+use nix::unistd::Pid;
+
 const UPDATE_FILE: &str = "/data/update";
 const LISTEN_SOCKET: &str = "[::]:12808";
 const MAGIC: [u8; 4] = [0x32, 0x7f, 0xfe, 0x4c];
@@ -283,9 +286,88 @@ fn check_connectivity(
 }
 
 fn rollback() -> io::Result<()> {
-    todo!()
+    switch_to_inactive_root()?;
+    reboot()
 }
 
 fn reboot() -> io::Result<()> {
-    todo!()
+    eprintln!("[info] connection unhealthy, rebooting");
+
+    match nix::sys::signal::kill(Pid::from_raw(1), Signal::SIGUSR1) {
+        Ok(_) => Ok(()),
+        Err(e) => Err(io::Error::from(e)),
+    }
+}
+
+fn modify_cmdline(new: &str) -> io::Result<()> {
+    let boot = boot_dev().ok_or(io::Error::from(io::ErrorKind::NotFound))?;
+    let boot_partition = std::fs::OpenOptions::new()
+        .read(true)
+        .write(true)
+        .open(boot)?;
+    let buf_stream = fscommon::BufStream::new(boot_partition);
+    let bootfs = fatfs::FileSystem::new(buf_stream, fatfs::FsOptions::new())?;
+
+    let mut file = bootfs.root_dir().open_file("cmdline.txt")?;
+
+    file.write_all(new.as_bytes())?;
+
+    Ok(())
+}
+
+fn dev() -> Option<&'static str> {
+    let devs = ["/dev/mmcblk0", "/dev/sda", "/dev/vda"];
+    devs.into_iter().find(|&dev| std::fs::metadata(dev).is_ok())
+}
+
+fn boot_dev() -> Option<&'static str> {
+    Some(match dev()? {
+        "/dev/mmcblk0" => "/dev/mmcblk0p1",
+        "/dev/sda" => "/dev/sda1",
+        "/dev/vda" => "/dev/vda1",
+        _ => unreachable!(),
+    })
+}
+
+fn inactive_root() -> io::Result<String> {
+    let cmdline = std::fs::read_to_string("/proc/cmdline")?;
+
+    for seg in cmdline.split(' ') {
+        if seg.starts_with("root=PARTUUID=00000000-") {
+            let root_id = match seg
+                .split("root=PARTUUID=00000000-0")
+                .collect::<Vec<&str>>()
+                .into_iter()
+                .next_back()
+                .expect("no root device")
+            {
+                "2" => "3",
+                "3" => "2",
+                _ => unreachable!(),
+            };
+
+            return Ok(
+                match dev().ok_or(io::Error::from(io::ErrorKind::NotFound))? {
+                    "/dev/mmcblk0" => format!("/dev/mmcblk0p{}", root_id),
+                    "/dev/sda" => format!("/dev/sda{}", root_id),
+                    "/dev/vda" => format!("/dev/vda{}", root_id),
+                    _ => unreachable!(),
+                },
+            );
+        }
+    }
+
+    Err(io::Error::from(io::ErrorKind::NotFound))
+}
+
+fn switch_to_inactive_root() -> io::Result<()> {
+    let new = inactive_root()?;
+    let new = String::from("root=PARTUUID=00000000-0") + &new.chars().last().unwrap().to_string();
+
+    let cmdline = format!("{} init=/bin/init rootwait console=tty1", new);
+
+    modify_cmdline(&cmdline)?;
+    nix::unistd::sync();
+
+    Ok(())
 }