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Subject[PATCH net-next V10] net: Variable SLAAC: SLAAC with prefixes of arbitrary length in PIO
Variable SLAAC:
[Disabled by default. Can be activated via sysctl]
["Race to the bottom" problem is solved]
SLAAC with prefixes of arbitrary length in PIO (randomly
generated hostID or stable privacy + privacy extensions).
The main problem is that SLAAC RA allocates a /64 by the Wireless
carrier 4G, 5G to a mobile hotspot, however segmentation of shorter net-
work prefix (ex. /48) is required so that downstream interfaces can be further
subnetted.
Example: uCPE device (4G + WI-FI enabled) receives /48 via Wireless, and
assigns /56 to VNF-Firewall, /56 to WIFI, /56 to Load-Balancer
and /56 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 <dmytro@shytyi.net>
---
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index ef4a69865737..076d99874797 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -79,6 +79,7 @@ struct ipv6_devconf {
__u32 ioam6_id;
__u32 ioam6_id_wide;
__u8 ioam6_enabled;
+ __s32 variable_slaac;

struct ctl_table_header *sysctl_header;
};
diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
index b243a53fa985..25606c267809 100644
--- a/include/uapi/linux/ipv6.h
+++ b/include/uapi/linux/ipv6.h
@@ -193,6 +193,7 @@ enum {
DEVCONF_IOAM6_ENABLED,
DEVCONF_IOAM6_ID,
DEVCONF_IOAM6_ID_WIDE,
+ DEVCONF_VARIABLE_SLAAC,
DEVCONF_MAX
};

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index c6a90b7bbb70..34a12d7f4fb8 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -241,6 +241,7 @@ static struct ipv6_devconf ipv6_devconf __read_mostly = {
.ioam6_enabled = 0,
.ioam6_id = IOAM6_DEFAULT_IF_ID,
.ioam6_id_wide = IOAM6_DEFAULT_IF_ID_WIDE,
+ .variable_slaac = 0,
};

static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
@@ -300,6 +301,7 @@ static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
.ioam6_enabled = 0,
.ioam6_id = IOAM6_DEFAULT_IF_ID,
.ioam6_id_wide = IOAM6_DEFAULT_IF_ID_WIDE,
+ .variable_slaac = 0,
};

/* Check if link is ready: is it up and is a valid qdisc available */
@@ -1349,9 +1351,15 @@ 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 < 64 &&
+ 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 *
@@ -2579,6 +2587,31 @@ 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,
@@ -2586,9 +2619,17 @@ 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 < 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 = {
@@ -2667,6 +2708,94 @@ 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)
+{
+ union data_union {
+ char __data[SHA1_BLOCK_SIZE];
+ struct {
+ struct in6_addr secret;
+ __be32 prefix[2];
+ unsigned char hwaddr[MAX_ADDR_LEN];
+ u8 dad_count;
+ } __packed;
+ };
+ union data_union *data;
+ struct in6_addr *secret;
+ struct in6_addr *temp;
+ struct net *net;
+ int *workspace;
+ int *digest;
+
+ workspace = kmalloc_array(SHA1_WORKSPACE_WORDS, sizeof(__u32), GFP_KERNEL);
+ digest = kmalloc_array(SHA1_DIGEST_WORDS, sizeof(__u32), GFP_KERNEL);
+ data = kmalloc(sizeof(*data), GFP_KERNEL);
+ secret = kmalloc(sizeof(*secret), GFP_KERNEL);
+ temp = kmalloc(sizeof(*temp), GFP_KERNEL);
+ net = dev_net(idev->dev);
+
+ 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:
+ 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);
+ }
+
+ 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;
@@ -2791,9 +2920,33 @@ 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 > 0 && pinfo->prefix_len < 64 &&
+ 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:
@@ -5542,6 +5679,7 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf,
array[DEVCONF_IOAM6_ENABLED] = cnf->ioam6_enabled;
array[DEVCONF_IOAM6_ID] = cnf->ioam6_id;
array[DEVCONF_IOAM6_ID_WIDE] = cnf->ioam6_id_wide;
+ array[DEVCONF_VARIABLE_SLAAC] = cnf->variable_slaac;
}

static inline size_t inet6_ifla6_size(void)
@@ -6905,6 +7043,13 @@ static const struct ctl_table addrconf_sysctl[] = {
.proc_handler = proc_dointvec,

},
+ {
+ .procname = "variable_slaac",
+ .data = &ipv6_devconf.variable_slaac,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ },
{
.procname = "seg6_enabled",
.data = &ipv6_devconf.seg6_enabled,
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