From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sat, 31 Jul 2021 13:05:47 +0000 (+0100)
Subject: mimeswap
X-Git-Tag: hippotat/1.0.0~416
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ian/git?a=commitdiff_plain;h=f9c716f0d611053c8d442e6e08105df7e27d4484;p=hippotat.git

mimeswap

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---

diff --git a/src/bin/client.rs b/src/bin/client.rs
index 9ba9b80..5f2362c 100644
--- a/src/bin/client.rs
+++ b/src/bin/client.rs
@@ -130,7 +130,9 @@ async fn run_client<C:HCC>(
             let mut packet =
               packet.context("read from ipif")?
               .ok_or_else(|| io::Error::from(io::ErrorKind::UnexpectedEof))?;
-            if let Ok(()) = slip::check_checkmtu_mimeswap(&ic, SLIP_ESC, &mut packet) {
+            if let Ok(()) = slip::check_checkmtu_mimeswap
+              ::<true>(&ic, &mut packet)
+            {
               let new_upbound_total = packet.len() + upbound_total + 1;
               if new_upbound_total > ic.max_batch_up.sat() {
                 tx_defer = Some(packet);
diff --git a/src/prelude.rs b/src/prelude.rs
index c51cdba..48febde 100644
--- a/src/prelude.rs
+++ b/src/prelude.rs
@@ -53,6 +53,6 @@ pub const SLIP_END:     u8 = 0o300;
 pub const SLIP_ESC:     u8 = 0o333;
 pub const SLIP_ESC_END: u8 = 0o334;
 pub const SLIP_ESC_ESC: u8 = 0o335;
-pub const SLIP_SWAP_ESC: u8 = b'-';
+pub const SLIP_MIME_ESC: u8 = b'-';
 
 pub fn default<T:Default>() -> T { Default::default() }
diff --git a/src/slip.rs b/src/slip.rs
index 7fe3542..b7be70b 100644
--- a/src/slip.rs
+++ b/src/slip.rs
@@ -7,31 +7,24 @@ use crate::prelude::*;
 pub static SLIP_END_SLICE: &[u8] = &[SLIP_END];
 
 #[throws(AE)]
-pub fn check_checkmtu_mimeswap(ic: &InstanceConfig, input_esc: u8,
-                               mut data: &mut [u8]) {
-  let mut sofar = 0;
-  let checkmtu = |_| Ok::<_,AE>(()); // xxx
-  while let Some((i, &c)) = data.iter().enumerate().find(
-    |(_,&c)| c == SLIP_ESC || c == SLIP_SWAP_ESC
-  ) {
-    let ni; let nc;
-    if c == input_esc {
-      match data.get(i+1) {
+pub fn check_checkmtu_mimeswap<const TO_MIME: bool>
+  (ic: &InstanceConfig, data: &mut [u8])
+{
+  for mut packet in data.split_mut(|&c| c == SLIP_END) {
+    if packet.len() > ic.mtu.sat() {
+      throw!(anyhow!("mtu exceeded ({} > {})", packet.len(), ic.mtu));
+    }
+
+    while let Some((i, _)) = packet.iter().enumerate().find(
+      |(_,&c)| c == if TO_MIME { SLIP_ESC } else { SLIP_MIME_ESC }
+    ) {
+      packet[i] = if TO_MIME { SLIP_MIME_ESC } else { SLIP_ESC };
+      match packet.get(i+1) {
         Some(&SLIP_ESC_END) |
         Some(&SLIP_ESC_ESC) => Ok(()),
         _ => Err(anyhow!("SLIP escape not followed by ESC_END or ESC_ESC")),
       }?;
-      ni = i+2;
-      sofar += ni;
-      nc = if input_esc == SLIP_ESC { SLIP_SWAP_ESC } else { SLIP_ESC };
-    } else {
-      ni = i+1;
-      sofar += ni;
-      checkmtu(sofar)?;
-      nc = input_esc;
-    };
-    data[i] = nc;
-    data = &mut data[ni ..];
+      packet = &mut packet[i+2 ..];
+    }
   }
-  checkmtu(data.len())?;
 }