Add min version check to avoid including old instances

Cargo.lock

@@ -418,7 +418,9 @@ dependencies = [
  "anyhow",
  "clap",
  "futures",
+ "once_cell",
  "reqwest",
+ "semver",
  "serde",
  "serde_json",
  "tokio",
@@ -521,9 +523,9 @@ dependencies = [
 
 [[package]]
 name = "once_cell"
-version = "1.7.2"
+version = "1.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "af8b08b04175473088b46763e51ee54da5f9a164bc162f615b91bc179dbf15a3"
+checksum = "87f3e037eac156d1775da914196f0f37741a274155e34a0b7e427c35d2a2ecb9"
 
 [[package]]
 name = "percent-encoding"
@@ -680,6 +682,12 @@ dependencies = [
  "untrusted",
 ]
 
+[[package]]
+name = "semver"
+version = "1.0.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d65bd28f48be7196d222d95b9243287f48d27aca604e08497513019ff0502cc4"
+
 [[package]]
 name = "serde"
 version = "1.0.124"

Cargo.toml

@@ -12,3 +12,5 @@ tokio = { version = "0.2.25", features = ["rt-threaded", "macros"] }
 futures = "0.3.13"
 serde_json = "1.0.64"
 clap = "2.33.3"
+semver = "1.0.7"
+once_cell = "1.10.0"

src/crawl.rs

@@ -4,10 +4,14 @@ use crate::REQUEST_TIMEOUT;
 use anyhow::anyhow;
 use anyhow::Error;
 use futures::try_join;
+use once_cell::sync::Lazy;
 use reqwest::Client;
+use semver::Version;
 use serde::Serialize;
 use std::collections::VecDeque;
 
+static CLIENT: Lazy<Client> = Lazy::new(Client::default);
+
 pub async fn crawl(
     start_instances: Vec<String>,
     exclude: Vec<String>,
@@ -17,6 +21,7 @@ pub async fn crawl(
         .iter()
         .map(|s| CrawlInstance::new(s.to_string(), 0))
         .collect();
+    let min_lemmy_version = min_lemmy_version().await?;
     let mut crawled_instances = vec![];
     let mut instance_details = vec![];
     let mut failed_instances = 0;
@@ -25,7 +30,7 @@ pub async fn crawl(
         if current_instance.depth > max_depth || exclude.contains(&current_instance.domain) {
             continue;
         }
-        match fetch_instance_details(&current_instance.domain).await {
+        match fetch_instance_details(&current_instance.domain, &min_lemmy_version).await {
             Ok(details) => {
                 instance_details.push(details.to_owned());
                 for i in details.linked_instances {
@@ -81,7 +86,10 @@ impl CrawlInstance {
     }
 }
 
-async fn fetch_instance_details(domain: &str) -> Result<InstanceDetails, Error> {
+async fn fetch_instance_details(
+    domain: &str,
+    min_lemmy_version: &Version,
+) -> Result<InstanceDetails, Error> {
     let client = Client::default();
 
     let node_info_url = format!("https://{}/nodeinfo/2.0.json", domain);
@@ -104,6 +112,13 @@ async fn fetch_instance_details(domain: &str) -> Result<InstanceDetails, Error>
         site_info_request_v3
     )?;
     let node_info: NodeInfo = node_info.json().await?;
+    if node_info.software.name != "lemmy" {
+        return Err(anyhow!("not a lemmy instance"));
+    }
+    let version = Version::parse(&node_info.software.version)?;
+    if &version < min_lemmy_version {
+        return Err(anyhow!("lemmy version is too old ({})", version));
+    }
     let site_info_v2 = site_info_v2.json::<GetSiteResponse>().await.ok();
     let site_info_v3 = site_info_v3.json::<GetSiteResponse>().await.ok();
     let mut site_info: GetSiteResponse = if let Some(site_info_v2) = site_info_v2 {
@@ -148,3 +163,18 @@ async fn fetch_instance_details(domain: &str) -> Result<InstanceDetails, Error>
         linked_instances,
     })
 }
+
+/// calculate minimum allowed lemmy version based on current version. in case of current version
+/// 0.16.3, the minimum from this function is 0.15.3. this is to avoid rejecting all instances on
+/// the previous version when a major lemmy release is published.
+async fn min_lemmy_version() -> Result<Version, Error> {
+    let lemmy_version_url = "https://raw.githubusercontent.com/LemmyNet/lemmy-ansible/main/VERSION";
+    let req = CLIENT
+        .get(lemmy_version_url)
+        .timeout(REQUEST_TIMEOUT)
+        .send()
+        .await?;
+    let mut version = Version::parse(req.text().await?.trim())?;
+    version.minor -= 1;
+    Ok(version)
+}