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

On Thu, Mar 2, 2023 at 6:58 PM 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(-)

diff --git a/cmd/Kconfig b/cmd/Kconfig index 2caa4af..c46613e 100644 --- a/cmd/Kconfig +++ b/cmd/Kconfig @@ -1894,6 +1894,13 @@ config CMD_NCSI Normally this happens automatically before other network operations.

+config IPV6_ROUTER_DISCOVERY

•   bool "Do router discovery"
  

•   depends on IPV6
  

•   help
  

•     Will automatically perform router solicitation on first IPv6
  

•     network operation
  

endif

config CMD_ETHSW diff --git a/include/ndisc.h b/include/ndisc.h index f6f8eb6..362d707 100644 --- a/include/ndisc.h +++ b/include/ndisc.h @@ -19,6 +19,20 @@ struct nd_msg { __u8 opt[0]; };

+/* struct rs_msg - ICMPv6 Router Solicitation message format */ +struct rs_msg {

•   struct icmp6hdr icmph;
  

•   __u8            opt[0];
  

+};

+/* struct ra_msg - ICMPv6 Router Advertisement message format */ +struct ra_msg {

•   struct icmp6hdr icmph;
  

•   __u32   reachable_time;
  

•   __u32   retransmission_timer;
  

•   __u8    opt[0];
  

+};

/* struct echo_msg - ICMPv6 echo request/reply message format */ struct echo_msg { struct icmp6hdr icmph; @@ -57,6 +71,11 @@ extern int net_nd_try; */ void ndisc_init(void);

+/*

• • ip6_send_rs() - Send IPv6 Router Solicitation Message
• */

+void ip6_send_rs(void);

/**

• ndisc_receive() - Handle ND packet

@@ -97,6 +116,10 @@ static inline int ndisc_timeout_check(void) { return 0; }

+void ip6_send_rs(void) +{ +} #endif

#endif /* __NDISC_H__ */ diff --git a/include/net.h b/include/net.h index 399af5e..25c43b3 100644 --- a/include/net.h +++ b/include/net.h @@ -505,7 +505,7 @@ extern int net_restart_wrap; /* Tried all network devices */

enum proto_t { BOOTP, RARP, ARP, TFTPGET, DHCP, PING, PING6, DNS, NFS, CDP, NETCONS,

•   SNTP, TFTPSRV, TFTPPUT, LINKLOCAL, FASTBOOT, WOL, UDP, NCSI, WGET
  

•   SNTP, TFTPSRV, TFTPPUT, LINKLOCAL, FASTBOOT, WOL, UDP, NCSI, WGET, RS
  

};

extern char net_boot_file_name[1024];/* Boot File name */ diff --git a/include/net6.h b/include/net6.h index 2d7c5a0..beafc05 100644 --- a/include/net6.h +++ b/include/net6.h @@ -81,8 +81,17 @@ struct udp_hdr { 0x00, 0x00, 0x00, 0x00, \ 0x00, 0x00, 0x00, 0x00, \ 0x00, 0x00, 0x00, 0x00 } } } +/*

• • All-routers multicast address is the link-local scope address to reach all
• • routers.
• */

+#define ALL_ROUTERS_MULT_ADDR { { { 0xFF, 0x02, 0x00, 0x00, \

•                             0x00, 0x00, 0x00, 0x00, \
  

•                             0x00, 0x00, 0x00, 0x00, \
  

•                             0x00, 0x00, 0x00, 0x02 } } }
  
  

#define IPV6_LINK_LOCAL_PREFIX 0xfe80 +#define IPV6_LINK_LOCAL_MASK 0xffb0 /* The first 10-bit of address mask. */

/* hop limit for neighbour discovery packets */ #define IPV6_NDISC_HOPLIMIT 255 @@ -166,6 +175,37 @@ struct icmp6hdr { #define icmp6_rt_lifetime icmp6_dataun.u_nd_ra.rt_lifetime } __packed;

+/*

• • struct icmp6_ra_prefix_info - Prefix Information option of the ICMPv6 message
• • The Prefix Information option provides hosts with on-link prefixes and
• • prefixes for Address Autoconfiguration. Refer to RFC 4861 for more info.
• */

+struct icmp6_ra_prefix_info {

•   u8      type;           /* Type is 3 for Prefix Information. */
  

•   u8      len;            /* Len is 4 for Prefix Information. */
  

•   /* The number of leading bits in the Prefix that are valid. */
  

•   u8      prefix_len;
  

•   u8      reserved1:6,    /* MUST be ignored by the receiver. */
  

•           aac:1,          /* autonomous address-configuration flag */
  

•   /* Indicates that this prefix can be used for on-link determination. */
  

•           on_link:1;
  

•   /*
  

•    * The length of time in seconds that the prefix is valid for the
  

•    * purpose of on-link determination.
  

•    */
  

•   __be32  valid_lifetime;
  

•   /* The length of time addresses remain preferred. */
  

•   __be32  preferred_lifetime;
  

•   __be32  reserved2;      /* MUST be ignored by the receiver. */
  

•   /*
  

•    * Prefix is an IP address or a prefix of an IP address. The Prefix
  

•    * Length field contains the number of valid leading bits in the prefix.
  

•    * The bits in the prefix after the prefix length are reserved and MUST
  

•    * be initialized to zero by the sender and ignored by the receiver.
  

•    */
  

•   struct in6_addr prefix;
  

+};

extern struct in6_addr const net_null_addr_ip6; /* NULL IPv6 address */ extern struct in6_addr net_gateway6; /* Our gateways IPv6 address */ extern struct in6_addr net_ip6; /* Our IPv6 addr (0 = unknown) */ diff --git a/net/ndisc.c b/net/ndisc.c index 367dae7..db76c4b 100644 --- a/net/ndisc.c +++ b/net/ndisc.c @@ -13,6 +13,8 @@ #include <net.h> #include <net6.h> #include <ndisc.h> +#include <stdlib.h> +#include <linux/delay.h>

/* IPv6 destination address of packet waiting for ND */ struct in6_addr net_nd_sol_packet_ip6 = ZERO_IPV6_ADDR; @@ -29,31 +31,37 @@ int net_nd_tx_packet_size; ulong net_nd_timer_start; /* the number of requests we have sent so far */ int net_nd_try; +struct in6_addr all_routers = ALL_ROUTERS_MULT_ADDR;

+#define MAX_RTR_SOLICITATIONS 3 +/* The maximum time to delay sending the first router solicitation message. */ +#define MAX_SOLICITATION_DELAY 1 // 1 second +/* The time to wait before sending the next router solicitation message. */ +#define RTR_SOLICITATION_INTERVAL 4000 // 4 seconds

#define IP6_NDISC_OPT_SPACE(len) (((len) + 2 + 7) & ~7)

/**

• ndisc_insert_option() - Insert an option into a neighbor discovery packet

• • @ndisc: pointer to ND packet

• • @opt: pointer to the option element of the neighbor discovery packet
  • @type: option type to insert
  • @data: option data to insert
  • @len: data length
  • Return: the number of bytes inserted (which may be >= len)
  */

-static int -ndisc_insert_option(struct nd_msg *ndisc, int type, u8 *data, int len) +static int ndisc_insert_option(__u8 *opt, int type, u8 *data, int len) { int space = IP6_NDISC_OPT_SPACE(len);

•   ndisc->opt[0] = type;
  

•   ndisc->opt[1] = space >> 3;
  

•   memcpy(&ndisc->opt[2], data, len);
  

•   opt[0] = type;
  

•   opt[1] = space >> 3;
  

•   memcpy(&opt[2], data, len);
    len += 2;
  
    /* fill the remainder with 0 */
    if (space - len > 0)
  

•           memset(&ndisc->opt[len], '\0', space - len);
  

•           memset(&opt[len], '\0', space - len);
  
    return space;
  

} @@ -123,7 +131,7 @@ static void ip6_send_ns(struct in6_addr *neigh_addr)

    /* Set the target address and llsaddr option */
    net_copy_ip6(&msg->target, neigh_addr);

•   ndisc_insert_option(msg, ND_OPT_SOURCE_LL_ADDR, net_ethaddr,
  

•   ndisc_insert_option(msg->opt, ND_OPT_SOURCE_LL_ADDR, net_ethaddr,
                        INETHADDRSZ);
  
    /* checksum */
  

@@ -137,6 +145,76 @@ static void ip6_send_ns(struct in6_addr *neigh_addr) net_send_packet(net_tx_packet, (pkt - net_tx_packet)); }

+/*

• • ip6_send_rs() - Send IPv6 Router Solicitation Message.
• • A router solicitation is sent to discover a router. RS message creation is
• • based on RFC 4861 section 4.1. Router Solicitation Message Format.
• */

+void ip6_send_rs(void) +{

•   unsigned char enetaddr[6];
  

•   struct rs_msg *msg;
  

•   __u16 icmp_len;
  

•   uchar *pkt;
  

•   unsigned short csum;
  

•   unsigned int pcsum;
  

•   static unsigned int retry_count;
  

•   if (!ip6_is_unspecified_addr(&net_gateway6) &&
  

•       net_prefix_length != 0) {
  

•           net_set_state(NETLOOP_SUCCESS);
  

•           return;
  

•   } else if (retry_count >= MAX_RTR_SOLICITATIONS) {
  

•           net_set_state(NETLOOP_FAIL);
  

•           net_set_timeout_handler(0, 0);
  

•           retry_count = 0;
  

•           return;
  

•   }
  

•   printf("ROUTER SOLICITATION %d\n", retry_count + 1);
  

•   ip6_make_mult_ethdstaddr(enetaddr, &all_routers);
  

•   /*
  

•    * ICMP length is the size of ICMP header (8) + one option (8) = 16.
  

•    * The option is 2 bytes of type and length + 6 bytes for MAC.
  

•    */
  

•   icmp_len = sizeof(struct icmp6hdr) + IP6_NDISC_OPT_SPACE(INETHADDRSZ);
  

•   pkt = (uchar *)net_tx_packet;
  

•   pkt += net_set_ether(pkt, enetaddr, PROT_IP6);
  

•   pkt += ip6_add_hdr(pkt, &net_link_local_ip6, &all_routers, PROT_ICMPV6,
  

•                      IPV6_NDISC_HOPLIMIT, icmp_len);
  

•   /* ICMPv6 - RS */
  

•   msg = (struct rs_msg *)pkt;
  

•   msg->icmph.icmp6_type = IPV6_NDISC_ROUTER_SOLICITATION;
  

•   msg->icmph.icmp6_code = 0;
  

•   memset(&msg->icmph.icmp6_cksum, 0, sizeof(__be16));
  

•   memset(&msg->icmph.icmp6_unused, 0, sizeof(__be32));
  

•   /* Set the llsaddr option */
  

•   ndisc_insert_option(msg->opt, ND_OPT_SOURCE_LL_ADDR, net_ethaddr,
  

•                       INETHADDRSZ);
  

•   /* checksum */
  

•   pcsum = csum_partial((__u8 *)msg, icmp_len, 0);
  

•   csum = csum_ipv6_magic(&net_link_local_ip6, &all_routers,
  

•                          icmp_len, PROT_ICMPV6, pcsum);
  

•   msg->icmph.icmp6_cksum = csum;
  

•   pkt += icmp_len;
  

•   /* Wait up to 1 second if it is the first try to get the RA */
  

•   if (retry_count == 0)
  

•           udelay(((unsigned int)rand() % 1000000) * MAX_SOLICITATION_DELAY);
  

•   /* send it! */
  

•   net_send_packet(net_tx_packet, (pkt - net_tx_packet));
  

•   retry_count++;
  

•   net_set_timeout_handler(RTR_SOLICITATION_INTERVAL, ip6_send_rs);
  

+}

static void ip6_send_na(uchar *eth_dst_addr, struct in6_addr *neigh_addr, struct in6_addr *target) @@ -167,7 +245,7 @@ ip6_send_na(uchar *eth_dst_addr, struct in6_addr *neigh_addr, msg->icmph.icmp6_dataun.u_nd_advt.override = 1; /* Set the target address and lltargetaddr option */ net_copy_ip6(&msg->target, target);

•   ndisc_insert_option(msg, ND_OPT_TARGET_LL_ADDR, net_ethaddr,
  

•   ndisc_insert_option(msg->opt, ND_OPT_TARGET_LL_ADDR, net_ethaddr,
                        INETHADDRSZ);
  
    /* checksum */
  

@@ -223,6 +301,10 @@ int ndisc_timeout_check(void) return 1; }

+/*

• • ndisc_init() - Make initial steps for ND state machine.
• • Usually move variables into initial state.
• */

void ndisc_init(void) { net_nd_packet_mac = NULL; @@ -234,12 +316,125 @@ void ndisc_init(void) net_nd_tx_packet -= (ulong)net_nd_tx_packet % PKTALIGN; }

+/*

• • validate_ra() - Validate the router advertisement message.
• • @ip6: Pointer to the router advertisement packet
• • @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;
  

•   /* ICMP checksum has already been checked in net_ip6_handler. */
  

•   if (icmp->icmp6_code != 0)
  

•           return false;
  

•   return true;
  

+}

+/*

• • process_ra() - Process the router advertisement packet.
• • @ip6: Pointer to the router advertisement packet
• • @len: Length of the router advertisement packet
• • Process the received router advertisement message.
• • Although RFC 4861 requires retaining at least two router addresses, we only
• • keep one because of the U-Boot limitations and its goal of lightweight code.
• • Return: 0 - RA is a default router and contains valid prefix information.
• • Non-zero - RA options are invalid or do not indicate it is a default router
• • or do not contain valid prefix information.
• */

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

•   /* Pointer to the ICMP section of the packet */
  

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

•   struct ra_msg *msg = (struct ra_msg *)icmp;
  

•   int remaining_option_len = len - IP6_HDR_SIZE - sizeof(struct ra_msg);
  

•   unsigned short int option_len;  /* Length of each option */
  

•   /* Pointer to the ICMPv6 message options */
  

•   unsigned char *option = NULL;
  

•   /* 8-bit identifier of the type of ICMPv6 option */
  

•   unsigned char type = 0;
  

•   struct icmp6_ra_prefix_info *prefix = NULL;
  

•   /* Ignore the packet if router lifetime is 0. */
  

•   if (!icmp->icmp6_rt_lifetime)
  

•           return -EOPNOTSUPP;
  

•   /* Processing the options */
  

•   option = msg->opt;
  

•   while (remaining_option_len > 0) {
  

•           /* The 2nd byte of the option is its length. */
  

•           option_len = option[1];
  

•           /* All included options should have a positive length. */
  

•           if (option_len == 0)
  

•                   return -EINVAL;
  

•           type = option[0];
  

•           /* All option types except Prefix Information are ignored. */
  

•           switch (type) {
  

•           case ND_OPT_SOURCE_LL_ADDR:
  

•           case ND_OPT_TARGET_LL_ADDR:
  

•           case ND_OPT_REDIRECT_HDR:
  

•           case ND_OPT_MTU:
  

•                   break;
  

•           case ND_OPT_PREFIX_INFO:
  

•                   prefix = (struct icmp6_ra_prefix_info *)option;
  

•                   /* The link-local prefix 0xfe80::/10 is ignored. */
  

•                   if ((ntohs(prefix->prefix.s6_addr16[0]) &
  

•                        IPV6_LINK_LOCAL_MASK) == IPV6_LINK_LOCAL_PREFIX)
  

•                           break;
  

•                   if (prefix->on_link && ntohl(prefix->valid_lifetime)) {
  

•                           net_prefix_length = prefix->prefix_len;
  

•                           net_gateway6 = ip6->saddr;
  

•                           return 0;
  

•                   }
  

•                   break;
  

•           default:
  

•                   debug("Unknown IPv6 Neighbor Discovery Option 0x%x\n",
  

•                         type);
  

•           }
  

•           option_len <<= 3; /* Option length is a multiple of 8. */
  

•           remaining_option_len -= option_len;
  

•           option += option_len;
  

•   }
  

•   return -EADDRNOTAVAIL;
  

+}

int ndisc_receive(struct ethernet_hdr *et, struct ip6_hdr *ip6, int len) { struct icmp6hdr *icmp = (struct icmp6hdr *)(((uchar *)ip6) + IP6_HDR_SIZE); struct nd_msg *ndisc = (struct nd_msg *)icmp; uchar neigh_eth_addr[6];

•   int err = 0;    // The error code returned calling functions.
  
    switch (icmp->icmp6_type) {
    case IPV6_NDISC_NEIGHBOUR_SOLICITATION:
  

@@ -280,6 +475,36 @@ int ndisc_receive(struct ethernet_hdr *et, struct ip6_hdr *ip6, int len) net_nd_packet_mac = NULL; } break;

•   case IPV6_NDISC_ROUTER_SOLICITATION:
  

•           break;
  

•   case IPV6_NDISC_ROUTER_ADVERTISEMENT:
  

•           debug("Received router advertisement for %pI6c from %pI6c\n",
  

•                 &ip6->daddr, &ip6->saddr);
  

•           /*
  

•            * If gateway and prefix are set, the RA packet is ignored. The
  

•            * reason is that the U-Boot code is supposed to be as compact
  

•            * as possible and does not need to take care of multiple
  

•            * routers. In addition to that, U-Boot does not want to handle
  

•            * scenarios like a router setting its lifetime to zero to
  

•            * indicate it is not routing anymore. U-Boot program has a
  

•            * short life when the system boots up and does not need such
  

•            * sophistication.
  

•            */
  

•           if (!ip6_is_unspecified_addr(&net_gateway6) &&
  

•               net_prefix_length != 0) {
  

•                   break;
  

•           }
  

•           if (!validate_ra(ip6, len)) {
  

•                   debug("Invalid router advertisement message.\n");
  

•                   break;
  

•           }
  

•           err = process_ra(ip6, len);
  

•           if (err)
  

•                   debug("Ignored router advertisement. Error: %d\n", err);
  

•           else
  

•                   printf("Set gatewayip6: %pI6c, prefix_length: %d\n",
  

•                          &net_gateway6, net_prefix_length);
  

•           break;
    default:
            debug("Unexpected ICMPv6 type 0x%x\n", icmp->icmp6_type);
            return -1;
  

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:

  • Prerequisites:  - own ethernet address
    

  • We want:        - own IP address
    

@@ -122,6 +122,7 @@ #endif #include <net/tcp.h> #include <net/wget.h> +#include "net_rand.h"

/** BOOTP EXTENTIONS **/

@@ -346,6 +347,8 @@ void net_auto_load(void)

static int net_init_loop(void) {

•   static bool first_call = true;
  

•   if (eth_get_dev()) {
            memcpy(net_ethaddr, eth_get_ethaddr(), 6);
  
  

@@ -365,6 +368,12 @@ static int net_init_loop(void) */ return -ENONET;

•   if (IS_ENABLED(CONFIG_IPV6_ROUTER_DISCOVERY))
  

•           if (first_call && use_ip6) {
  

•                   first_call = false;
  

•                   srand_mac(); /* This is for rand used in ip6_send_rs. */
  

•                   net_loop(RS);
  

•           }
    return 0;
  

}

@@ -574,6 +583,10 @@ restart: ncsi_probe_packages(); break; #endif

•           case RS:
  

•                   if (IS_ENABLED(CONFIG_IPV6_ROUTER_DISCOVERY))
  

•                           ip6_send_rs();
  

•                   break;
            default:
                    break;
            }
  

@@ -671,7 +684,13 @@ restart: x = time_handler; time_handler = (thand_f *)0; (*x)();

•           }
  

•           } else if (IS_ENABLED(CONFIG_IPV6_ROUTER_DISCOVERY))
  

•                   if (time_handler && protocol == RS)
  

•                           if (!ip6_is_unspecified_addr(&net_gateway6) &&
  

•                               net_prefix_length != 0) {
  

•                                   net_set_state(NETLOOP_SUCCESS);
  

•                                   net_set_timeout_handler(0, 0);
  

•                           }
  
            if (net_state == NETLOOP_FAIL)
                    ret = net_start_again();
  

diff --git a/net/net6.c b/net/net6.c index 75577bc..2dd64c0 100644 --- a/net/net6.c +++ b/net/net6.c @@ -413,6 +413,7 @@ int net_ip6_handler(struct ethernet_hdr *et, struct ip6_hdr *ip6, int len) break; case IPV6_NDISC_NEIGHBOUR_SOLICITATION: case IPV6_NDISC_NEIGHBOUR_ADVERTISEMENT:

•           case IPV6_NDISC_ROUTER_ADVERTISEMENT:
                    ndisc_receive(et, ip6, len);
                    break;
            default:
  

-- 1.8.3.1

Reviewed-by: Ramon Fried rfried.dev@gmail.com