It'd be great if someone more familiar with our IPv6 code could take a
look. Adding some folks to the CC.
On Wed, 16 Dec 2020 23:01:29 +0100 Dmytro Shytyi wrote:
> Variable SLAAC [Can be activated via sysctl]:
> SLAAC with prefixes of arbitrary length in PIO (randomly
> generated hostID or stable privacy + privacy extensions).
> The main problem is that SLAAC RA or PD allocates a /64 by the Wireless
> carrier 4G, 5G to a mobile hotspot, however segmentation of the /64 via
> SLAAC is required so that downstream interfaces can be further subnetted.
> Example: uCPE device (4G + WI-FI enabled) receives /64 via Wireless, and
> assigns /72 to VNF-Firewall, /72 to WIFI, /72 to Load-Balancer
> and /72 to wired connected devices.
> IETF document that defines problem statement:
> draft-mishra-v6ops-variable-slaac-problem-stmt
> IETF document that specifies variable slaac:
> draft-mishra-6man-variable-slaac
>
> Signed-off-by: Dmytro Shytyi <dmy...@shytyi.net>
The RFC mentions checking a flag in RA, but I don't see that in this
patch, could you explain?
> diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
> index 13e8751bf24a..f2af4f9fba2d 100644
> --- a/include/uapi/linux/ipv6.h
> +++ b/include/uapi/linux/ipv6.h
> @@ -189,7 +189,8 @@ enum {
> DEVCONF_ACCEPT_RA_RT_INFO_MIN_PLEN,
> DEVCONF_NDISC_TCLASS,
> DEVCONF_RPL_SEG_ENABLED,
> - DEVCONF_MAX
> + DEVCONF_MAX,
MAX should be the last field, no? Isn't it used for sizing tables?
> + DEVCONF_VARIABLE_SLAAC
> };
>
>
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index eff2cacd5209..4afaf2bc8d8b 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -236,6 +236,7 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = {
> .addr_gen_mode = IN6_ADDR_GEN_MODE_EUI64,
> .disable_policy = 0,
> .rpl_seg_enabled = 0,
> + .variable_slaac = 0,
> };
>
> static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
> @@ -291,6 +292,7 @@ static struct ipv6_devconf ipv6_devconf_dflt
> __read_mostly = {
> .addr_gen_mode = IN6_ADDR_GEN_MODE_EUI64,
> .disable_policy = 0,
> .rpl_seg_enabled = 0,
> + .variable_slaac = 0,
> };
>
> /* Check if link is ready: is it up and is a valid qdisc available */
> @@ -1340,9 +1342,15 @@ static int ipv6_create_tempaddr(struct inet6_ifaddr
> *ifp, bool block)
> goto out;
> }
> in6_ifa_hold(ifp);
> - memcpy(addr.s6_addr, ifp->addr.s6_addr, 8);
> - ipv6_gen_rnd_iid(&addr);
>
> + if (ifp->prefix_len == 64) {
> + memcpy(addr.s6_addr, ifp->addr.s6_addr, 8);
> + ipv6_gen_rnd_iid(&addr);
> + } else if (ifp->prefix_len > 0 && ifp->prefix_len <= 128 &&
> + idev->cnf.variable_slaac) {
> + get_random_bytes(addr.s6_addr, 16);
> + ipv6_addr_prefix_copy(&addr, &ifp->addr, ifp->prefix_len);
> + }
> age = (now - ifp->tstamp) / HZ;
>
> regen_advance = idev->cnf.regen_max_retry *
> @@ -2569,6 +2577,31 @@ static bool is_addr_mode_generate_stable(struct
> inet6_dev *idev)
> idev->cnf.addr_gen_mode == IN6_ADDR_GEN_MODE_RANDOM;
> }
>
> +static struct inet6_ifaddr *ipv6_cmp_rcvd_prsnt_prfxs(struct inet6_ifaddr
> *ifp,
> + struct inet6_dev *in6_dev,
> + struct net *net,
> + const struct prefix_info
> *pinfo)
> +{
> + struct inet6_ifaddr *result = NULL;
> + bool prfxs_equal;
> +
> + rcu_read_lock();
> + list_for_each_entry_rcu(ifp, &in6_dev->addr_list, if_list) {
> + if (!net_eq(dev_net(ifp->idev->dev), net))
> + continue;
> + prfxs_equal =
> + ipv6_prefix_equal(&pinfo->prefix, &ifp->addr,
> pinfo->prefix_len);
> + if (prfxs_equal && pinfo->prefix_len == ifp->prefix_len) {
> + result = ifp;
> + in6_ifa_hold(ifp);
> + break;
> + }
> + }
> + rcu_read_unlock();
> +
> + return result;
> +}
> +
> int addrconf_prefix_rcv_add_addr(struct net *net, struct net_device *dev,
> const struct prefix_info *pinfo,
> struct inet6_dev *in6_dev,
> @@ -2576,9 +2609,17 @@ int addrconf_prefix_rcv_add_addr(struct net *net,
> struct net_device *dev,
> u32 addr_flags, bool sllao, bool tokenized,
> __u32 valid_lft, u32 prefered_lft)
> {
> - struct inet6_ifaddr *ifp = ipv6_get_ifaddr(net, addr, dev, 1);
> + struct inet6_ifaddr *ifp = NULL;
> + int plen = pinfo->prefix_len;
> int create = 0;
>
> + if (plen > 0 && plen <= 128 && plen != 64 &&
> + in6_dev->cnf.addr_gen_mode != IN6_ADDR_GEN_MODE_STABLE_PRIVACY &&
> + in6_dev->cnf.variable_slaac)
> + ifp = ipv6_cmp_rcvd_prsnt_prfxs(ifp, in6_dev, net, pinfo);
> + else
> + ifp = ipv6_get_ifaddr(net, addr, dev, 1);
> +
> if (!ifp && valid_lft) {
> int max_addresses = in6_dev->cnf.max_addresses;
> struct ifa6_config cfg = {
> @@ -2657,6 +2698,90 @@ int addrconf_prefix_rcv_add_addr(struct net *net,
> struct net_device *dev,
> }
> EXPORT_SYMBOL_GPL(addrconf_prefix_rcv_add_addr);
>
> +static bool ipv6_reserved_interfaceid(struct in6_addr address)
> +{
> + if ((address.s6_addr32[2] | address.s6_addr32[3]) == 0)
> + return true;
> +
> + if (address.s6_addr32[2] == htonl(0x02005eff) &&
> + ((address.s6_addr32[3] & htonl(0xfe000000)) == htonl(0xfe000000)))
> + return true;
> +
> + if (address.s6_addr32[2] == htonl(0xfdffffff) &&
> + ((address.s6_addr32[3] & htonl(0xffffff80)) == htonl(0xffffff80)))
> + return true;
> +
> + return false;
> +}
> +
> +static int ipv6_gen_addr_var_plen(struct in6_addr *address,
> + u8 dad_count,
> + const struct inet6_dev *idev,
> + unsigned int rcvd_prfx_len,
> + bool stable_privacy_mode)
> +{
> + static union {
> + char __data[SHA1_BLOCK_SIZE];
> + struct {
> + struct in6_addr secret;
> + __be32 prefix[2];
> + unsigned char hwaddr[MAX_ADDR_LEN];
> + u8 dad_count;
> + } __packed;
> + } data;
> + static __u32 workspace[SHA1_WORKSPACE_WORDS];
> + static __u32 digest[SHA1_DIGEST_WORDS];
> + struct net *net = dev_net(idev->dev);
> + static DEFINE_SPINLOCK(lock);
> + struct in6_addr secret;
> + struct in6_addr temp;
> +
> + BUILD_BUG_ON(sizeof(data.__data) != sizeof(data));
> +
> + if (stable_privacy_mode) {
> + if (idev->cnf.stable_secret.initialized)
> + secret = idev->cnf.stable_secret.secret;
> + else if (net->ipv6.devconf_dflt->stable_secret.initialized)
> + secret = net->ipv6.devconf_dflt->stable_secret.secret;
> + else
> + return -1;
> + }
> +
> +retry:
> + spin_lock_bh(&lock);
> + if (stable_privacy_mode) {
> + sha1_init(digest);
> + memset(&data, 0, sizeof(data));
> + memset(workspace, 0, sizeof(workspace));
> + memcpy(data.hwaddr, idev->dev->perm_addr, idev->dev->addr_len);
> + data.prefix[0] = address->s6_addr32[0];
> + data.prefix[1] = address->s6_addr32[1];
> + data.secret = secret;
> + data.dad_count = dad_count;
> +
> + sha1_transform(digest, data.__data, workspace);
> +
> + temp.s6_addr32[0] = (__force __be32)digest[0];
> + temp.s6_addr32[1] = (__force __be32)digest[1];
> + temp.s6_addr32[2] = (__force __be32)digest[2];
> + temp.s6_addr32[3] = (__force __be32)digest[3];
> + } else {
> + get_random_bytes(temp.s6_addr32, 16);
> + }
> +
> + spin_unlock_bh(&lock);
Is there a reason this code declares all this state on the stack and
protects it with a lock rather than just allocating the memory with
kmalloc()?
> + if (ipv6_reserved_interfaceid(temp)) {
> + dad_count++;
> + if (dad_count > dev_net(idev->dev)->ipv6.sysctl.idgen_retries)
> + return -1;
> + goto retry;
> + }
> + ipv6_addr_prefix_copy(&temp, address, rcvd_prfx_len);
> + *address = temp;
> + return 0;
> +}
> +
> void addrconf_prefix_rcv(struct net_device *dev, u8 *opt, int len, bool
> sllao)
> {
> struct prefix_info *pinfo;
> @@ -2781,9 +2906,34 @@ void addrconf_prefix_rcv(struct net_device *dev, u8
> *opt, int len, bool sllao)
> dev_addr_generated = true;
> }
> goto ok;
> + } else if (pinfo->prefix_len != 64 &&
> + pinfo->prefix_len > 0 && pinfo->prefix_len <= 128 &&
> + in6_dev->cnf.variable_slaac) {
> + /* SLAAC with prefixes of arbitrary length (Variable
> SLAAC).
> + * draft-mishra-6man-variable-slaac
> + * draft-mishra-v6ops-variable-slaac-problem-stmt
> + */
> + memcpy(&addr, &pinfo->prefix, 16);
> + if (in6_dev->cnf.addr_gen_mode ==
> IN6_ADDR_GEN_MODE_STABLE_PRIVACY) {
> + if (!ipv6_gen_addr_var_plen(&addr,
> + 0,
> + in6_dev,
> + pinfo->prefix_len,
> + true)) {
> + addr_flags |= IFA_F_STABLE_PRIVACY;
> + goto ok;
> + }
> + } else if (!ipv6_gen_addr_var_plen(&addr,
> + 0,
> + in6_dev,
> + pinfo->prefix_len,
> + false)) {
> + goto ok;
> + }
> + } else {
> + net_dbg_ratelimited("IPv6: Prefix with unexpected
> length %d\n",
> + pinfo->prefix_len);
> }
> - net_dbg_ratelimited("IPv6 addrconf: prefix with wrong length
> %d\n",
> - pinfo->prefix_len);
> goto put;
>
> ok:
> @@ -3186,22 +3336,6 @@ void addrconf_add_linklocal(struct inet6_dev *idev,
> }
> EXPORT_SYMBOL_GPL(addrconf_add_linklocal);
>
> -static bool ipv6_reserved_interfaceid(struct in6_addr address)
> -{
> - if ((address.s6_addr32[2] | address.s6_addr32[3]) == 0)
> - return true;
> -
> - if (address.s6_addr32[2] == htonl(0x02005eff) &&
> - ((address.s6_addr32[3] & htonl(0xfe000000)) == htonl(0xfe000000)))
> - return true;
> -
> - if (address.s6_addr32[2] == htonl(0xfdffffff) &&
> - ((address.s6_addr32[3] & htonl(0xffffff80)) == htonl(0xffffff80)))
> - return true;
> -
> - return false;
> -}
> -
> static int ipv6_generate_stable_address(struct in6_addr *address,
> u8 dad_count,
> const struct inet6_dev *idev)
> @@ -5517,6 +5651,7 @@ static inline void ipv6_store_devconf(struct
> ipv6_devconf *cnf,
> array[DEVCONF_DISABLE_POLICY] = cnf->disable_policy;
> array[DEVCONF_NDISC_TCLASS] = cnf->ndisc_tclass;
> array[DEVCONF_RPL_SEG_ENABLED] = cnf->rpl_seg_enabled;
> + array[DEVCONF_VARIABLE_SLAAC] = cnf->variable_slaac;
> }
>
> static inline size_t inet6_ifla6_size(void)
> @@ -6897,6 +7032,13 @@ static const struct ctl_table addrconf_sysctl[] = {
> .mode = 0644,
> .proc_handler = proc_dointvec,
> },
> + {
> + .procname = "variable_slaac",
> + .data = &ipv6_devconf.variable_slaac,
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = proc_dointvec,
> + },
> {
> /* sentinel */
> }
