NuttX has supported the Internet Protocol Version 4 (IPv4) for many years. There have been fragments of IPv6 in the code base for many years as well, but these fragments were not more than place markers and not functional.
But recently, post NuttX-7.6, I have focused some effort into completing the IPv6 implementation. This Wiki page contains notes from that integration effort and will, hopefully, evolve to provide full documentation for NuttX IPv6 support.
Current status: Basic functionality is complete and verified. That includes ICMPPv6 Neighbor Discover Protocol, IPCMPv6 Echo Request/Response (for ping6), TCP/IPv6, and UDP/IPv6. It has also been proven that you can support a platform with both IPv4 and IPv6 enabled.
In order to support IPv6, Ethernet drivers must do the following:
ipv6_input in order to pass the packets into the network stack. This is equivalent to calling ipv4_input when an IPv4 pack is received.neighbor_out() in order to add the MAC address of the destination into the link layer header. IPv6's ICMPv6 Neighbor Discovery Protocol is the moral equivalent of the Address Resolution Protocol (ARP) used with IPv6. And the IPv6 neighbor_out() performs a similar function to the IPv4 arp_out() function.All existing NuttX Ethernet drivers have already been modified to support the requirements of the first two bullets. However, additional logic must be added to most of the existing Ethernet drivers to support the final requirement.
Each Ethernet device connects to the Ethernet wire via a PHY and so potentially has access to every packet that passes on the wire. In promiscuous mode, that is the behavior that is desired but normally it is not: The amount of traffic that appears on the wire would swamp most modest MCUs in promiscuous mode. So instead, the Ethernet MAC hardware will support address filtering. That is, the hardware will look at the Ethernet header at the beginning of each packet and will ignore packets that do not have the desired information in the Ethernet header. The software will see only those filtered packets that are desired.
Typically, the Ethernet MAC is set-up for unicast address filtering: The hardware is programmed so that that only packets whose destination Ethernet MAC address matches the MAC address programmed into the hardware are accepted. In addition, special broadcast Ethernet addresses will also be accepted. In this way, the volume of Ethernet data received by the MCU is greatly reduced.
Multicast addresses are a little different. Unlike broadcast addresses, there are many possible multicast addresses and so the Ethernet MAC hardware must support some special capability to match the destination Ethernet address in an incoming packet with a variety of multicast addresses. Usually this involves hashing the Ethernet address and performing a hash table lookup to check for an address match.
Each Ethernet driver uses a common interface that is defined in nuttx/include/nuttx/net/netdev.h. That interface defines, among other things, a set of calls into the Ethernet driver to perform a variety of functions. One of those functions is multicast address filtering:
#ifdef CONFIG_NET_IGMP
int (*d_addmac)(FAR struct net_driver_s *dev, FAR const uint8_t *mac);
int (*d_rmmac)(FAR struct net_driver_s *dev, FAR const uint8_t *mac);
#endif
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The d_addmac() interface adds a multicast address to the hash table; d_rmmac() removes a multicast address from the hash table.
These interface is only required if IGMP is supported, but the underlying ability to program multicast address filtered is required for full IPv6 support. This interface exists in all Ethernet drivers but most are currently place holders and are to-be-provided. At present, only the STMicro STM32, the TI Tiva TM4C, and the Atmel SAM3/4 and SAMA5D3/4 Ethernet drivers support multicast hash tables. This capability will have to be added to any additional Ethernet drivers that are modified to support IPv6.
The ICMPv6 Neighbor Discover protocol is the reason for this additional address filtering. The ICMPv6 Neighbor Discovery Protocol is the replacement for IPv4's ARP. It differents from ARP in the it is implemented not at the Ethernet link layer, but within the IPv6 layer. In order to receive broadcast packets to ICMPv6, the IPv6 Multicast address of 33.33.ff.xx.xx.xx is used, where the xx.xx.xx part derives from the IPv6 address. The Ethernet driver filtering logic must be modified so that it accepts packets directed to the that MAC address.
At present, this additional support is only implemented for the TI Tiva TM4C129X Ethernet driver. Below is a snippet of code from that drier showing how this is implemented:
/* Set the MAC address */
tiva_macaddress(priv);
#ifdef CONFIG_NET_ICMPv6
/* Set up the IPv6 multicast address */
tiva_ipv6multicast(priv);
#endif
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Where tiva_macaddress() sets up the normal MAC address filtering and tiva_ipv6multicast() sets up the special filtering needed by IPv6:
/****************************************************************************
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#ifdef CONFIG_NET_ICMPv6
static void tiva_ipv6multicast(FAR struct tiva_ethmac_s *priv)
{
struct net_driver_s *dev;
uint16_t tmp16;
uint8_t mac[6];
/* For ICMPv6, we need to add the IPv6 multicast address
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mac[0] = 0x33;
mac[1] = 0x33;
dev = &priv->dev;
tmp16 = dev->d_ipv6addr[6];
mac[2] = 0xff;
mac[3] = tmp16 >> 8;
tmp16 = dev->d_ipv6addr[7];
mac[4] = tmp16 & 0xff;
mac[5] = tmp16 >> 8;
nvdbg("IPv6 Multicast: %02x:%02x:%02x:%02x:%02x:%02x\n",
mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
(void)tiva_addmac(dev, mac);
#ifdef CONFIG_NET_ICMPv6_AUTOCONF
/* Add the IPv6 all link-local nodes Ethernet address. This is the
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(void)tiva_addmac(dev, g_ipv6_ethallnodes.ether_addr_octet);
#endif /* CONFIG_NET_ICMPv6_AUTOCONF */
#ifdef CONFIG_NET_ICMPv6_ROUTER
/* Add the IPv6 all link-local routers Ethernet address. This is the
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(void)tiva_addmac(dev, g_ipv6_ethallrouters.ether_addr_octet);
#endif /* CONFIG_NET_ICMPv6_ROUTER */
}
#endif /* CONFIG_NET_ICMPv6 */
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The following Ethernet drivers are complete and IPv6 ready. All others Ethernet drivers have all required IPv6 support except that they are missing (1) the required ICMPv6 addressing filtering described above and/or (2) support for multi-cast address filtering.
At present, there are three board configuration that are pre-configured to use IPv6: nuttx/boards/arm/tiva/dk-tm4c129x/configs/ipv6, {{ nuttx/boards/arm/stm32/stm32f4discovery/ipv6}}, and nuttx/boards/arm/tiva/tm4c1294-launchpad/configs/ipv6. These default configurations have only IPv6 enabled. But the README files at in those board directories describes how to enable both IPv4 and IPv6 simultaneously.
ping -6 fc00::2
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ping6 fc00::2
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nsh> ping6 fc00::2
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CONFIG_NET_IPv4=y and CONFIG_NET_IPv6=n
nsh> ifconfig
eth0 Link encap: Ethernet HWaddr 00:1a:b6:02:81:14 at UP
inet addr:10.0.0.2 DRaddr:10.0.0.1 Mask:255.255.255.0
IPv4 TCP UDP ICMP
Received 003b 001c 0000 0004
Dropped 001b 0000 0000 0000
IPv4 VHL: 0000 Frg: 0000
Checksum 0000 0000 0000 ----
TCP ACK: 0000 SYN: 0000
RST: 0000 0000
Type 0000 ---- ---- 0000
Sent 0031 002d 0000 0004
Rexmit ---- ---- 0000 ----
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NOTE: The detailed packet statistics only appear if CONFIG_NET_STATISTICS is enabled.
CONFIG_NET_IPv4=n and CONFIG_NET_IPv6=y
nsh> ifconfig
eth0 Link encap: Ethernet HWaddr 00:1a:b6:02:81:14 at UP
inet6 addr:fc00::2
inet6 DRaddr:fc00::1
inet6 Mask:ffff:ffff:ffff::ffff:ffff:ffff:ff80
IPv6 TCP UDP ICMPv6
Received 0007 0000 0000 0007
Dropped 0000 0000 0000 0000
IPv6 VHL: 0000
Checksum ---- 0000 0000 ----
TCP ACK: 0000 SYN: 0000
RST: 0000 0000
Type 0000 ---- ---- 0000
Sent 0011 0000 0000 0011
Rexmit ---- ---- 0000 ----
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CONFIG_NET_IPv4=y and CONFIG_NET_IPv6=y
nsh> ifconfig
eth0 Link encap: Ethernet HWaddr 00:1a:b6:02:81:14 at UP
inet addr:10.0.0.2 DRaddr:10.0.0.1 Mask:255.255.255.0
inet6 addr:fc00::2
inet6 DRaddr:fc00::1
inet6 Mask:ffff:ffff:ffff::ffff:ffff:ffff:ff80
IPv4 IPv6 TCP UDP ICMP ICMPv6
Received 0047 000a 001c 0000 0004 000a
Dropped 0027 0000 0000 0000 0000 0000
IPv4 VHL: 0000 Frg: 0000
IPv6 VHL: 0000
Checksum 0000 ---- 0000 0000 ---- ----
TCP ACK: 0000 SYN: 0000
RST: 0000 0000
Type 0000 0000 ---- ---- 0000 0000
Sent 0033 000a 002f 0000 0004 000a
Rexmit ---- ---- ---- 0000 ---- ----
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In addition to the core RTOS support IPv6, changes are also required to networking tests, to networking aware applications, and, of course, to all of the network utils (netutils).
ping6 command has been added. But there are many commands that still require updating.apps/examples. The nettest test and the udp test have been adapted to work in the IPv6 domain, but none of the others have yet been adapted.apps/netutils have been adapted to work with IPv6: DHCP, FTP, TFTP, Telnet, etc. Support for managing IPv6 address have been included in the netlib, but nothing else has yet been updated.