Add missing comments for GetNetworkParametersFromNAD

pkg/octavia/network_parameters.go

@@ -50,9 +50,15 @@ func getConfigFromNAD(
 	return nadConfig, nil
 }
 
+// getRangeFromCIDR - compute a IP address range from a CIDR
 func getRangeFromCIDR(
 	cidr netip.Prefix,
 ) (start netip.Addr, end netip.Addr) {
+	// For IPv6, a /64 is expected, if the CIDR is aaaa:bbbb:cccc:dddd::/64,
+	// the range is aaaa:bbbb:cccc:dddd::5 - aaaa:bbbb:cccc:dddd:ffff:ffff:ffff:fffe
+	// For IPv4, a /16 is expected, if the CIDR is a.b.0.0/16
+	// the range is a.b.0.5 - a.b.255.254
+	// IPs from from 1 to 5 are reserved for later user
 	addr := cidr.Addr()
 	if addr.Is6() {
 		addrBytes := addr.As16()
@@ -78,6 +84,7 @@ func getRangeFromCIDR(
 	return
 }
 
+// GetNetworkParametersFromNAD - Extract network information from the Network Attachment Definition
 func GetNetworkParametersFromNAD(
 	nad *networkv1.NetworkAttachmentDefinition,
 ) (*NetworkParameters, error) {
@@ -89,8 +96,14 @@ func GetNetworkParametersFromNAD(
 	}
 
 	// Provider subnet parameters
+	// These are the parameters for octavia-provider-net/subnet
 	networkParameters.ProviderCIDR = nadConfig.IPAM.CIDR
 
+	// OpenShift allocates IP addresses from IPAM.RangeStart to IPAM.RangeEnd
+	// for the pods.
+	// We're going to use a range of 25 IP addresses that are assigned to
+	// the Neutron allocation pool, the range starts right after OpenShift
+	// RangeEnd.
 	networkParameters.ProviderAllocationStart = nadConfig.IPAM.RangeEnd.Next()
 	end := networkParameters.ProviderAllocationStart
 	for i := 0; i < LbProvSubnetPoolSize; i++ {
@@ -100,14 +113,21 @@ func GetNetworkParametersFromNAD(
 		end = end.Next()
 	}
 	networkParameters.ProviderAllocationEnd = end
+
+	// The default gateway of the provider network is the gateway of our route
 	if len(nadConfig.IPAM.Routes) > 0 {
 		networkParameters.ProviderGateway = nadConfig.IPAM.Routes[0].Gateway
 	} else {
 		return nil, fmt.Errorf("cannot find gateway information in network attachment")
 	}
 
-	// Tenant subnet parameters
+	// Tenant subnet parameters - parameters for lb-mgmt-net/subnet
+	// The NAD must contain one route to the Octavia Tenant Management network,
+	// the gateway is an IP address of the provider network and the destination
+	// is the CIDR of the Tenant network.
 	networkParameters.TenantCIDR = nadConfig.IPAM.Routes[0].Destination
+
+	// For IPv4, we require a /16 subnet, for IPv6 a /64
 	var bitlen int
 	if networkParameters.TenantCIDR.Addr().Is6() {
 		bitlen = 64
@@ -119,6 +139,7 @@ func GetNetworkParametersFromNAD(
 		return nil, fmt.Errorf("the tenant CIDR is /%d, it should be /%d", networkParameters.TenantCIDR.Bits(), bitlen)
 	}
 
+	// Compute an allocation range based on the CIDR
 	start, end := getRangeFromCIDR(networkParameters.TenantCIDR)
 	networkParameters.TenantAllocationStart = start
 	networkParameters.TenantAllocationEnd = end