Re: [PATCH] net: ipv6: Add support for default gateway discovery.

On Thu, 2023-03-02 at 08:58 -0800, emohandesi@linux.microsoft.com wrote:

From: Ehsan Mohandesi emohandesi@microsoft.com

In IPv6, the default gateway and prefix length are determined by receiving a router advertisement as defined in - https://www.rfc-editor.org/rfc/rfc4861.

Add support for sending router solicitation (RS) and processing router advertisements (RA).

If the RA has prefix info option and following conditions are met, then gatewayip6 and net_prefix_length of ip6addr env variables are initialized. These are later consumed by IPv6 code for non-local destination IP.

• "Router Lifetime" != 0
• Prefix is NOT link-local prefix (0xfe80::/10)
• L flag is 1
• "Valid Lifetime" != 0

Timing Parameters:

• MAX_RTR_SOLICITATION_DELAY (0-1s)
• RTR_SOLICITATION_INTERVAL (4s) (min retransmit delay)
• MAX_RTR_SOLICITATIONS (3 RS transmissions)

The functionality is enabled by CONFIG_IPV6_ROUTER_DISCOVERY and invoked automatically from net_init_loop().

Signed-off-by: Ehsan Mohandesi emohandesi@microsoft.com

Conflicts: cmd/Kconfig include/net.h net/net.c

---

cmd/Kconfig | 7 ++ include/ndisc.h | 23 ++++++ include/net.h | 2 +- include/net6.h | 40 ++++++++++ net/ndisc.c | 243 +++++++++++++++++++++++++++++++++++++++++++++++++++++--- net/net.c | 23 +++++- net/net6.c | 1 + 7 files changed, 327 insertions(+), 12 deletions(-)

I reviewed this patch and it looks good. I have no critical remarks, only some small notes.

I've tested it on SiFive Unmatched board.

+config IPV6_ROUTER_DISCOVERY

•   bool "Do router discovery"
  

•   depends on IPV6
  

•   help
  

•     Will automatically perform router solicitation on first
  

IPv6

•     network operation
  

endif

I think it is better to write sth like Do IPv6 router discovery because IPv4 has also router discovery protocol and it could lead to misunderstanding

net_set_timeout_handler(0, 0);

Maybe net_set_timeout_handler(0, NULL); is better

+/*

• • validate_ra() - Validate the router advertisement message.
• • @ip6:
• • @len: Length of the router advertisement packet
• • Check if the router advertisement message is valid. Conditions

are

• • according to RFC 4861 section 6.1.2. Validation of Router

Advertisement

• • Messages.
• • Return: true if the message is valid and false if it is invalid.
• */

+static bool validate_ra(struct ip6_hdr *ip6, int len) +{

•   struct icmp6hdr *icmp = (struct icmp6hdr *)(ip6 + 1);
  

•   /* ICMP length (derived from the IP length) should be 16 or
  

more octets. */

•   if (ip6->payload_len < 16)
  

•           return false;
  

•   /* Source IP Address should be a valid link-local address. */
  

•   if ((ntohs(ip6->saddr.s6_addr16[0]) & IPV6_LINK_LOCAL_MASK)
  

!=

•       IPV6_LINK_LOCAL_PREFIX)
  

•           return false;
  

•   /*
  

•    * The IP Hop Limit field should have a value of 255, i.e.,
  

the packet

•    * could not possibly have been forwarded by a router.
  

•    */
  

•   if (ip6->hop_limit != 255)
  

•           return false;
  

Unicast hop limit only?

diff --git a/net/net.c b/net/net.c index c9a749f..39f0b81 100644 --- a/net/net.c +++ b/net/net.c @@ -24,7 +24,7 @@

•                 - name of bootfile
  

• Next step:      ARP
  

• • LINK_LOCAL:

• • LINKLOCAL:

Maybe it is better to move to other patch?!

Reviewed-by: Viacheslav Mitrofanov v.v.mitrofanov@yadro.com Tested-by: Viacheslav Mitrofanov v.v.mitrofanov@yadro.com