vsock: Fail to parse VsockArgs if duplicate CIDs specified

Currently, while updating the `cid_map`, it is not checked if the map
already contained a key with the same CID before. So, fail to parse
VsockArgs if there exist multiple VMs configured with the same CID.

Signed-off-by: Priyansh Rathi <techiepriyansh@gmail.com>

crates/vsock/src/main.rs

@@ -9,7 +9,7 @@ mod vhu_vsock_thread;
 mod vsock_conn;
 
 use std::{
-    collections::HashMap,
+    collections::{HashMap, HashSet},
     convert::TryFrom,
     process::exit,
     sync::{Arc, RwLock},
@@ -35,6 +35,8 @@ enum CliError {
     NoArgsProvided,
     #[error("Failed to parse configuration file")]
     ConfigParse,
+    #[error("Multiple VMs configured with the same CID: {0}")]
+    DuplicateCids(u64),
 }
 
 #[derive(Debug, ThisError)]
@@ -194,8 +196,8 @@ impl TryFrom<VsockArgs> for Vec<VsockConfig> {
     type Error = CliError;
 
     fn try_from(cmd_args: VsockArgs) -> Result<Self, CliError> {
-        // we try to use the configuration first, if failed,  then fall back to the manual settings.
-        match cmd_args.parse_config() {
+        let configs = match cmd_args.parse_config() {
+            // we try to use the configuration first, if failed,  then fall back to the manual settings.
             Some(c) => c,
             _ => match cmd_args.vm {
                 Some(v) => Ok(v),
@@ -209,7 +211,18 @@ impl TryFrom<VsockArgs> for Vec<VsockConfig> {
                     )])
                 }),
             },
+        }?;
+
+        // check if there are duplicate CIDs
+        let mut cid_set: HashSet<u64> = HashSet::new();
+        for c in &configs {
+            let cid = c.get_guest_cid();
+            if !cid_set.insert(cid) {
+                return Err(CliError::DuplicateCids(cid));
+            }
         }
+
+        Ok(configs)
     }
 }
 
@@ -432,6 +445,27 @@ mod tests {
             vec!["group2".to_string(), "group3".to_string()]
         );
 
+        // Test parse failure with duplicate CIDs
+        let params = format!(
+            "--vm socket={vhost3_socket},uds_path={vm3_vsock} \
+             --vm socket={vhost4_socket},uds-path={vm4_vsock},guest-cid=3,tx_buffer_size=65536,groups=group1 \
+             --vm groups=group2+group3,guest-cid=5,socket={vhost5_socket},uds_path={vm5_vsock},tx-buffer-size=32768",
+            vhost3_socket = socket_paths[0].display(),
+            vhost4_socket = socket_paths[1].display(),
+            vhost5_socket = socket_paths[2].display(),
+            vm3_vsock = uds_paths[0].display(),
+            vm4_vsock = uds_paths[1].display(),
+            vm5_vsock = uds_paths[2].display(),
+        );
+
+        let mut params = params.split_whitespace().collect::<Vec<&str>>();
+        params.insert(0, "");
+
+        let args = VsockArgs::parse_from(params);
+
+        let configs = Vec::<VsockConfig>::try_from(args);
+        assert!(configs.is_err());
+
         test_dir.close().unwrap();
     }