Added feature to set the hop limit for mcast

libcoap/src/error.rs

@@ -23,6 +23,13 @@ pub enum MulticastGroupJoinError {
     Unknown,
 }
 
+#[derive(Error, Debug, Copy, Clone, Eq, PartialEq)]
+pub enum MulticastHopLimitError {
+    /// Unknown error inside of libcoap
+    #[error("CoAP multicast hop limit error: unable to set hop limit for multicast")]
+    Unknown,
+}
+
 #[derive(Error, Debug, Copy, Clone, Eq, PartialEq)]
 pub enum EndpointCreationError {
     /// Unknown error inside of libcoap

libcoap/src/session/mod.rs

@@ -19,8 +19,8 @@ use std::{
 };
 
 use libcoap_sys::{
-    coap_context_t, coap_fixed_point_t, coap_mid_t, coap_new_message_id, coap_pdu_get_token, coap_pdu_t,
-    coap_response_t, coap_response_t_COAP_RESPONSE_FAIL, coap_response_t_COAP_RESPONSE_OK, coap_send,
+    coap_context_t, coap_fixed_point_t, coap_mcast_set_hops, coap_mid_t, coap_new_message_id, coap_pdu_get_token,
+    coap_pdu_t, coap_response_t, coap_response_t_COAP_RESPONSE_FAIL, coap_response_t_COAP_RESPONSE_OK, coap_send,
     coap_session_get_ack_random_factor, coap_session_get_ack_timeout, coap_session_get_addr_local,
     coap_session_get_addr_remote, coap_session_get_ifindex, coap_session_get_max_retransmit, coap_session_get_proto,
     coap_session_get_state, coap_session_get_type, coap_session_init_token, coap_session_max_pdu_size,
@@ -38,7 +38,7 @@ use libcoap_sys::{coap_session_get_psk_hint, coap_session_get_psk_identity, coap
 use self::sealed::{CoapSessionCommonInternal, CoapSessionInnerProvider};
 pub use self::{client::CoapClientSession, server::CoapServerSession};
 use crate::{
-    error::{MessageConversionError, SessionGetAppDataError},
+    error::{MessageConversionError, MulticastHopLimitError, SessionGetAppDataError},
     message::{request::CoapRequest, response::CoapResponse, CoapMessage, CoapMessageCommon},
     protocol::CoapToken,
     types::{CoapAddress, CoapMessageId, CoapProtocol, IfIndex, MaxRetransmit},
@@ -296,6 +296,19 @@ pub trait CoapSessionCommon<'a>: CoapSessionCommonInternal<'a> {
         unsafe { coap_session_set_mtu(self.inner_mut().raw_session, mtu) }
     }
 
+    /// Sets maximum number of hops for multicast request
+    fn set_mcast_hops_limit(&self, hops: usize) -> Result<(), MulticastHopLimitError> {
+        // In some cases the default hoplimit of 1 is not enough to reach the destination. Choose limit accordingly
+        // SAFETY: Provided session pointer being valid is an invariant of CoapSessionInner
+        unsafe {
+            let ret = coap_mcast_set_hops(self.inner_mut().raw_session, hops);
+            if ret == 0 {
+                return Err(MulticastHopLimitError::Unknown);
+            }
+        };
+        Ok(())
+    }
+
     /// Returns the next message ID that should be used for this session.
     fn next_message_id(&self) -> CoapMessageId {
         // SAFETY: Provided session pointer being valid is an invariant of CoapSessionInner