net: socket: Add support for adjusting IPv4 TTL

The IPv4 TTL could only manipulated via net_context interface.
It makes sense to allow the same from socket interface via
the setsockopt/getsockopt calls.

Signed-off-by: Jukka Rissanen <[email protected]>

Author: jukkar

include/zephyr/net/net_context.h

@@ -1137,6 +1137,7 @@ enum net_context_option {
 	NET_OPT_MCAST_TTL         = 13,
 	NET_OPT_MCAST_HOP_LIMIT   = 14,
 	NET_OPT_UNICAST_HOP_LIMIT = 15,
+	NET_OPT_TTL               = 16,
 };
 
 /**

include/zephyr/net/socket.h

@@ -1100,6 +1100,9 @@ struct ifreq {
 /** sockopt: Set or receive the Type-Of-Service value for an outgoing packet. */
 #define IP_TOS 1
 
+/** sockopt: Set or receive the Time-To-Live value for an outgoing packet. */
+#define IP_TTL 2
+
 /** sockopt: Pass an IP_PKTINFO ancillary message that contains a
  *  pktinfo structure that supplies some information about the
  *  incoming packet.

subsys/net/ip/net_context.c

@@ -48,6 +48,12 @@ LOG_MODULE_REGISTER(net_ctx, CONFIG_NET_CONTEXT_LOG_LEVEL);
 #define INITIAL_MCAST_TTL 1
 #endif
 
+#ifdef CONFIG_NET_INITIAL_TTL
+#define INITIAL_TTL CONFIG_NET_INITIAL_TTL
+#else
+#define INITIAL_TTL 1
+#endif
+
 #ifdef CONFIG_NET_INITIAL_MCAST_HOP_LIMIT
 #define INITIAL_MCAST_HOP_LIMIT CONFIG_NET_INITIAL_MCAST_HOP_LIMIT
 #else
@@ -501,6 +507,7 @@ int net_context_get(sa_family_t family, enum net_sock_type type, uint16_t proto,
 					break;
 				}
 
+				contexts[i].ipv4_ttl = INITIAL_TTL;
 				contexts[i].ipv4_mcast_ttl = INITIAL_MCAST_TTL;
 			}
 		}
@@ -1097,7 +1104,6 @@ int net_context_create_ipv4_new(struct net_context *context,
 		}
 	}
 
-	net_pkt_set_ipv4_ttl(pkt, net_context_get_ipv4_ttl(context));
 #if defined(CONFIG_NET_CONTEXT_DSCP_ECN)
 	net_pkt_set_ip_dscp(pkt, net_ipv4_get_dscp(context->options.dscp_ecn));
 	net_pkt_set_ip_ecn(pkt, net_ipv4_get_ecn(context->options.dscp_ecn));
@@ -1565,6 +1571,26 @@ static int get_context_dscp_ecn(struct net_context *context,
 #endif
 }
 
+static int get_context_ttl(struct net_context *context,
+				 void *value, size_t *len)
+{
+#if defined(CONFIG_NET_IPV4)
+	*((int *)value) = context->ipv4_ttl;
+
+	if (len) {
+		*len = sizeof(int);
+	}
+
+	return 0;
+#else
+	ARG_UNUSED(context);
+	ARG_UNUSED(value);
+	ARG_UNUSED(len);
+
+	return -ENOTSUP;
+#endif
+}
+
 static int get_context_mcast_ttl(struct net_context *context,
 				 void *value, size_t *len)
 {
@@ -2793,6 +2819,24 @@ static int set_context_dscp_ecn(struct net_context *context,
 #endif
 }
 
+static int set_context_ttl(struct net_context *context,
+			   const void *value, size_t len)
+{
+#if defined(CONFIG_NET_IPV4)
+	uint8_t ttl = *((int *)value);
+
+	len = sizeof(context->ipv4_ttl);
+
+	return set_uint8_option(&context->ipv4_ttl, &ttl, len);
+#else
+	ARG_UNUSED(context);
+	ARG_UNUSED(value);
+	ARG_UNUSED(len);
+
+	return -ENOTSUP;
+#endif
+}
+
 static int set_context_mcast_ttl(struct net_context *context,
 				 const void *value, size_t len)
 {
@@ -2961,6 +3005,9 @@ int net_context_set_option(struct net_context *context,
 	case NET_OPT_DSCP_ECN:
 		ret = set_context_dscp_ecn(context, value, len);
 		break;
+	case NET_OPT_TTL:
+		ret = set_context_ttl(context, value, len);
+		break;
 	case NET_OPT_MCAST_TTL:
 		ret = set_context_mcast_ttl(context, value, len);
 		break;
@@ -3028,6 +3075,9 @@ int net_context_get_option(struct net_context *context,
 	case NET_OPT_DSCP_ECN:
 		ret = get_context_dscp_ecn(context, value, len);
 		break;
+	case NET_OPT_TTL:
+		ret = get_context_ttl(context, value, len);
+		break;
 	case NET_OPT_MCAST_TTL:
 		ret = get_context_mcast_ttl(context, value, len);
 		break;

subsys/net/lib/sockets/sockets.c

@@ -2518,6 +2518,16 @@ int zsock_getsockopt_ctx(struct net_context *ctx, int level, int optname,
 
 			break;
 
+		case IP_TTL:
+			ret = net_context_get_option(ctx, NET_OPT_TTL,
+						     optval, optlen);
+			if (ret < 0) {
+				errno  = -ret;
+				return -1;
+			}
+
+			return 0;
+
 		case IP_MULTICAST_TTL:
 			ret = net_context_get_option(ctx, NET_OPT_MCAST_TTL,
 						     optval, optlen);
@@ -2926,6 +2936,16 @@ int zsock_setsockopt_ctx(struct net_context *ctx, int level, int optname,
 				return -1;
 			}
 
+			return 0;
+
+		case IP_TTL:
+			ret = net_context_set_option(ctx, NET_OPT_TTL,
+						     optval, optlen);
+			if (ret < 0) {
+				errno  = -ret;
+				return -1;
+			}
+
 			return 0;
 		}