Optimized Favicon downloading

Some optimizations in regards to downloading Favicon's.

I also encounterd some issues with accessing some sites where the
connection got dropped or closed early. This seems a reqwest/hyper
thingy, https://github.com/hyperium/hyper/issues/2136. This is now also
fixed.

General:

- Decreased struct size
- Decreased memory allocations
- Optimized tokenizer a bit more to only emit tags when all attributes are there and are valid.

reqwest/hyper connection issue:
The following changes helped solve the connection issues to some sites.
The endresult is that some icons are now able to be downloaded always instead of sometimes.

- Enabled some extra reqwest features, `deflate` and `native-tls-alpn`
  (Which do not bring in any extra crates since other crates already enabled them, but they were not active for Vaultwarden it self)
- Configured reqwest to have a max amount of idle pool connections per host
- Configured reqwest to timeout the idle connections in 10 seconds

2 files changed, 116 insertions, 108 deletions

diff --git a/Cargo.toml b/Cargo.toml
index ce211917..6875db8a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -124,7 +124,7 @@ email_address = "0.2.4"
 handlebars = { version = "4.3.7", features = ["dir_source"] }
 
 # HTTP client (Used for favicons, version check, DUO and HIBP API)
-reqwest = { version = "0.11.18", features = ["stream", "json", "gzip", "brotli", "socks", "cookies", "trust-dns"] }
+reqwest = { version = "0.11.18", features = ["stream", "json", "deflate", "gzip", "brotli", "socks", "cookies", "trust-dns", "native-tls-alpn"] }
 
 # Favicon extraction libraries
 html5gum = "0.5.7"
diff --git a/src/api/icons.rs b/src/api/icons.rs
index dcf985f7..124f3a8f 100644
--- a/src/api/icons.rs
+++ b/src/api/icons.rs
@@ -19,7 +19,7 @@ use tokio::{
     net::lookup_host,
 };
 
-use html5gum::{Emitter, EndTag, HtmlString, InfallibleTokenizer, Readable, StartTag, StringReader, Tokenizer};
+use html5gum::{Emitter, HtmlString, InfallibleTokenizer, Readable, StringReader, Tokenizer};
 
 use crate::{
     error::Error,
@@ -46,10 +46,15 @@ static CLIENT: Lazy<Client> = Lazy::new(|| {
     // Generate the cookie store
     let cookie_store = Arc::new(Jar::default());
 
+    let icon_download_timeout = Duration::from_secs(CONFIG.icon_download_timeout());
+    let pool_idle_timeout = Duration::from_secs(10);
     // Reuse the client between requests
     let client = get_reqwest_client_builder()
         .cookie_provider(Arc::clone(&cookie_store))
-        .timeout(Duration::from_secs(CONFIG.icon_download_timeout()))
+        .timeout(icon_download_timeout)
+        .pool_max_idle_per_host(5) // Configure the Hyper Pool to only have max 5 idle connections
+        .pool_idle_timeout(pool_idle_timeout) // Configure the Hyper Pool to timeout after 10 seconds
+        .trust_dns(true)
         .default_headers(default_headers.clone());
 
     match client.build() {
@@ -58,9 +63,11 @@ static CLIENT: Lazy<Client> = Lazy::new(|| {
             error!("Possible trust-dns error, trying with trust-dns disabled: '{e}'");
             get_reqwest_client_builder()
                 .cookie_provider(cookie_store)
-                .timeout(Duration::from_secs(CONFIG.icon_download_timeout()))
-                .default_headers(default_headers)
+                .timeout(icon_download_timeout)
+                .pool_max_idle_per_host(5) // Configure the Hyper Pool to only have max 5 idle connections
+                .pool_idle_timeout(pool_idle_timeout) // Configure the Hyper Pool to timeout after 10 seconds
                 .trust_dns(false)
+                .default_headers(default_headers)
                 .build()
                 .expect("Failed to build client")
         }
@@ -258,7 +265,7 @@ mod tests {
     }
 }
 
-#[derive(Debug, Clone)]
+#[derive(Clone)]
 enum DomainBlacklistReason {
     Regex,
     IP,
@@ -415,38 +422,34 @@ fn get_favicons_node(
     const TAG_LINK: &[u8] = b"link";
     const TAG_BASE: &[u8] = b"base";
     const TAG_HEAD: &[u8] = b"head";
-    const ATTR_REL: &[u8] = b"rel";
     const ATTR_HREF: &[u8] = b"href";
     const ATTR_SIZES: &[u8] = b"sizes";
 
     let mut base_url = url.clone();
-    let mut icon_tags: Vec<StartTag> = Vec::new();
+    let mut icon_tags: Vec<Tag> = Vec::new();
     for token in dom {
-        match token {
-            FaviconToken::StartTag(tag) => {
-                if *tag.name == TAG_LINK
-                    && tag.attributes.contains_key(ATTR_REL)
-                    && tag.attributes.contains_key(ATTR_HREF)
-                {
-                    let rel_value = std::str::from_utf8(tag.attributes.get(ATTR_REL).unwrap())
-                        .unwrap_or_default()
-                        .to_ascii_lowercase();
-                    if rel_value.contains("icon") && !rel_value.contains("mask-icon") {
-                        icon_tags.push(tag);
-                    }
-                } else if *tag.name == TAG_BASE && tag.attributes.contains_key(ATTR_HREF) {
-                    let href = std::str::from_utf8(tag.attributes.get(ATTR_HREF).unwrap()).unwrap_or_default();
+        let tag_name: &[u8] = &token.tag.name;
+        match tag_name {
+            TAG_LINK => {
+                icon_tags.push(token.tag);
+            }
+            TAG_BASE => {
+                base_url = if let Some(href) = token.tag.attributes.get(ATTR_HREF) {
+                    let href = std::str::from_utf8(href).unwrap_or_default();
                     debug!("Found base href: {href}");
-                    base_url = match base_url.join(href) {
+                    match base_url.join(href) {
                         Ok(inner_url) => inner_url,
-                        _ => url.clone(),
-                    };
-                }
+                        _ => continue,
+                    }
+                } else {
+                    continue;
+                };
             }
-            FaviconToken::EndTag(tag) => {
-                if *tag.name == TAG_HEAD {
-                    break;
-                }
+            TAG_HEAD if token.closing => {
+                break;
+            }
+            _ => {
+                continue;
             }
         }
     }
@@ -820,43 +823,64 @@ impl reqwest::cookie::CookieStore for Jar {
 }
 
 /// Custom FaviconEmitter for the html5gum parser.
-/// The FaviconEmitter is using an almost 1:1 copy of the DefaultEmitter with some small changes.
+/// The FaviconEmitter is using an optimized version of the DefaultEmitter.
 /// This prevents emitting tags like comments, doctype and also strings between the tags.
+/// But it will also only emit the tags we need and only if they have the correct attributes
 /// Therefor parsing the HTML content is faster.
-use std::collections::{BTreeSet, VecDeque};
+use std::collections::BTreeMap;
+
+#[derive(Default)]
+pub struct Tag {
+    /// The tag's name, such as `"link"` or `"base"`.
+    pub name: HtmlString,
 
-#[derive(Debug)]
-enum FaviconToken {
-    StartTag(StartTag),
-    EndTag(EndTag),
+    /// A mapping for any HTML attributes this start tag may have.
+    ///
+    /// Duplicate attributes are ignored after the first one as per WHATWG spec.
+    pub attributes: BTreeMap<HtmlString, HtmlString>,
 }
 
-#[derive(Default, Debug)]
+struct FaviconToken {
+    tag: Tag,
+    closing: bool,
+}
+
+#[derive(Default)]
 struct FaviconEmitter {
     current_token: Option<FaviconToken>,
     last_start_tag: HtmlString,
     current_attribute: Option<(HtmlString, HtmlString)>,
-    seen_attributes: BTreeSet<HtmlString>,
-    emitted_tokens: VecDeque<FaviconToken>,
+    emit_token: bool,
 }
 
 impl FaviconEmitter {
-    fn emit_token(&mut self, token: FaviconToken) {
-        self.emitted_tokens.push_front(token);
-    }
+    fn flush_current_attribute(&mut self, emit_current_tag: bool) {
+        const ATTR_HREF: &[u8] = b"href";
+        const ATTR_REL: &[u8] = b"rel";
+        const TAG_LINK: &[u8] = b"link";
+        const TAG_BASE: &[u8] = b"base";
+        const TAG_HEAD: &[u8] = b"head";
+
+        if let Some(ref mut token) = self.current_token {
+            let tag_name: &[u8] = &token.tag.name;
+
+            if self.current_attribute.is_some() && (tag_name == TAG_BASE || tag_name == TAG_LINK) {
+                let (k, v) = self.current_attribute.take().unwrap();
+                token.tag.attributes.entry(k).and_modify(|_| {}).or_insert(v);
+            }
 
-    fn flush_current_attribute(&mut self) {
-        if let Some((k, v)) = self.current_attribute.take() {
-            match self.current_token {
-                Some(FaviconToken::StartTag(ref mut tag)) => {
-                    tag.attributes.entry(k).and_modify(|_| {}).or_insert(v);
-                }
-                Some(FaviconToken::EndTag(_)) => {
-                    self.seen_attributes.insert(k);
-                }
-                _ => {
-                    debug_assert!(false);
+            let tag_attr = &token.tag.attributes;
+            match tag_name {
+                TAG_HEAD if token.closing => self.emit_token = true,
+                TAG_BASE if tag_attr.contains_key(ATTR_HREF) => self.emit_token = true,
+                TAG_LINK if emit_current_tag && tag_attr.contains_key(ATTR_REL) && tag_attr.contains_key(ATTR_HREF) => {
+                    let rel_value =
+                        std::str::from_utf8(token.tag.attributes.get(ATTR_REL).unwrap()).unwrap_or_default();
+                    if rel_value.contains("icon") && !rel_value.contains("mask-icon") {
+                        self.emit_token = true
+                    }
                 }
+                _ => (),
             }
         }
     }
@@ -871,87 +895,71 @@ impl Emitter for FaviconEmitter {
     }
 
     fn pop_token(&mut self) -> Option<Self::Token> {
-        self.emitted_tokens.pop_back()
+        if self.emit_token {
+            self.emit_token = false;
+            return self.current_token.take();
+        }
+        None
     }
 
     fn init_start_tag(&mut self) {
-        self.current_token = Some(FaviconToken::StartTag(StartTag::default()));
+        self.current_token = Some(FaviconToken {
+            tag: Tag::default(),
+            closing: false,
+        });
     }
 
     fn init_end_tag(&mut self) {
-        self.current_token = Some(FaviconToken::EndTag(EndTag::default()));
-        self.seen_attributes.clear();
+        self.current_token = Some(FaviconToken {
+            tag: Tag::default(),
+            closing: true,
+        });
     }
 
     fn emit_current_tag(&mut self) -> Option<html5gum::State> {
-        self.flush_current_attribute();
-        let mut token = self.current_token.take().unwrap();
-        let mut emit = false;
-        match token {
-            FaviconToken::EndTag(ref mut tag) => {
-                // Always clean seen attributes
-                self.seen_attributes.clear();
-                self.set_last_start_tag(None);
-
-                // Only trigger an emit for the </head> tag.
-                // This is matched, and will break the for-loop.
-                if *tag.name == b"head" {
-                    emit = true;
-                }
-            }
-            FaviconToken::StartTag(ref mut tag) => {
-                // Only trriger an emit for <link> and <base> tags.
-                // These are the only tags we want to parse.
-                if *tag.name == b"link" || *tag.name == b"base" {
-                    self.set_last_start_tag(Some(&tag.name));
-                    emit = true;
-                } else {
-                    self.set_last_start_tag(None);
-                }
-            }
-        }
-
-        // Only emit the tags we want to parse.
-        if emit {
-            self.emit_token(token);
+        self.flush_current_attribute(true);
+        self.last_start_tag.clear();
+        if self.current_token.is_some() && !self.current_token.as_ref().unwrap().closing {
+            self.last_start_tag.extend(&*self.current_token.as_ref().unwrap().tag.name);
         }
-        None
+        html5gum::naive_next_state(&self.last_start_tag)
     }
 
     fn push_tag_name(&mut self, s: &[u8]) {
-        match self.current_token {
-            Some(
-                FaviconToken::StartTag(StartTag {
-                    ref mut name,
-                    ..
-                })
-                | FaviconToken::EndTag(EndTag {
-                    ref mut name,
-                    ..
-                }),
-            ) => {
-                name.extend(s);
-            }
-            _ => debug_assert!(false),
+        if let Some(ref mut token) = self.current_token {
+            token.tag.name.extend(s);
         }
     }
 
     fn init_attribute(&mut self) {
-        self.flush_current_attribute();
-        self.current_attribute = Some(Default::default());
+        self.flush_current_attribute(false);
+        self.current_attribute = match &self.current_token {
+            Some(token) => {
+                let tag_name: &[u8] = &token.tag.name;
+                match tag_name {
+                    b"link" | b"head" | b"base" => Some(Default::default()),
+                    _ => None,
+                }
+            }
+            _ => None,
+        };
     }
 
     fn push_attribute_name(&mut self, s: &[u8]) {
-        self.current_attribute.as_mut().unwrap().0.extend(s);
+        if let Some(attr) = &mut self.current_attribute {
+            attr.0.extend(s)
+        }
     }
 
     fn push_attribute_value(&mut self, s: &[u8]) {
-        self.current_attribute.as_mut().unwrap().1.extend(s);
+        if let Some(attr) = &mut self.current_attribute {
+            attr.1.extend(s)
+        }
     }
 
     fn current_is_appropriate_end_tag_token(&mut self) -> bool {
-        match self.current_token {
-            Some(FaviconToken::EndTag(ref tag)) => !self.last_start_tag.is_empty() && self.last_start_tag == tag.name,
+        match &self.current_token {
+            Some(token) if token.closing => !self.last_start_tag.is_empty() && self.last_start_tag == token.tag.name,
             _ => false,
         }
     }