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mpls: Netlink commands to add, remove, and dump routes
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This change adds two new netlink routing attributes:
RTA_VIA and RTA_NEWDST.

RTA_VIA specifies the specifies the next machine to send a packet to
like RTA_GATEWAY.  RTA_VIA differs from RTA_GATEWAY in that it
includes the address family of the address of the next machine to send
a packet to.  Currently the MPLS code supports addresses in AF_INET,
AF_INET6 and AF_PACKET.  For AF_INET and AF_INET6 the destination mac
address is acquired from the neighbour table.  For AF_PACKET the
destination mac_address is specified in the netlink configuration.

I think raw destination mac address support with the family AF_PACKET
will prove useful.  There is MPLS-TP which is defined to operate
on machines that do not support internet packets of any flavor.  Further
seem to be corner cases where it can be useful.  At this point
I don't care much either way.

RTA_NEWDST specifies the destination address to forward the packet
with.  MPLS typically changes it's destination address at every hop.
For a swap operation RTA_NEWDST is specified with a length of one label.
For a push operation RTA_NEWDST is specified with two or more labels.
For a pop operation RTA_NEWDST is not specified or equivalently an emtpy
RTAN_NEWDST is specified.

Those new netlink attributes are used to implement handling of rt-netlink
RTM_NEWROUTE, RTM_DELROUTE, and RTM_GETROUTE messages, to maintain the
MPLS label table.

rtm_to_route_config parses a netlink RTM_NEWROUTE or RTM_DELROUTE message,
verify no unhandled attributes or unhandled values are present and sets
up the data structures for mpls_route_add and mpls_route_del.

I did my best to match up with the existing conventions with the caveats
that MPLS addresses are all destination-specific-addresses, and so
don't properly have a scope.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Eric W. Biederman authored and David S. Miller committed Mar 4, 2015
1 parent 966bae3 commit 03c0566
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8 changes: 8 additions & 0 deletions include/uapi/linux/rtnetlink.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -303,6 +303,8 @@ enum rtattr_type_t {
RTA_TABLE,
RTA_MARK,
RTA_MFC_STATS,
RTA_VIA,
RTA_NEWDST,
__RTA_MAX
};

Expand Down Expand Up @@ -344,6 +346,12 @@ struct rtnexthop {
#define RTNH_SPACE(len) RTNH_ALIGN(RTNH_LENGTH(len))
#define RTNH_DATA(rtnh) ((struct rtattr*)(((char*)(rtnh)) + RTNH_LENGTH(0)))

/* RTA_VIA */
struct rtvia {
__kernel_sa_family_t rtvia_family;
__u8 rtvia_addr[0];
};

/* RTM_CACHEINFO */

struct rta_cacheinfo {
Expand Down
229 changes: 229 additions & 0 deletions net/mpls/af_mpls.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -212,6 +212,11 @@ static struct packet_type mpls_packet_type __read_mostly = {
.func = mpls_forward,
};

const struct nla_policy rtm_mpls_policy[RTA_MAX+1] = {
[RTA_DST] = { .type = NLA_U32 },
[RTA_OIF] = { .type = NLA_U32 },
};

struct mpls_route_config {
u32 rc_protocol;
u32 rc_ifindex;
Expand Down Expand Up @@ -410,6 +415,22 @@ static struct notifier_block mpls_dev_notifier = {
.notifier_call = mpls_dev_notify,
};

static int nla_put_via(struct sk_buff *skb,
u16 family, const void *addr, int alen)
{
struct nlattr *nla;
struct rtvia *via;

nla = nla_reserve(skb, RTA_VIA, alen + 2);
if (!nla)
return -EMSGSIZE;

via = nla_data(nla);
via->rtvia_family = family;
memcpy(via->rtvia_addr, addr, alen);
return 0;
}

int nla_put_labels(struct sk_buff *skb, int attrtype,
u8 labels, const u32 label[])
{
Expand Down Expand Up @@ -467,6 +488,210 @@ int nla_get_labels(const struct nlattr *nla,
return 0;
}

static int rtm_to_route_config(struct sk_buff *skb, struct nlmsghdr *nlh,
struct mpls_route_config *cfg)
{
struct rtmsg *rtm;
struct nlattr *tb[RTA_MAX+1];
int index;
int err;

err = nlmsg_parse(nlh, sizeof(*rtm), tb, RTA_MAX, rtm_mpls_policy);
if (err < 0)
goto errout;

err = -EINVAL;
rtm = nlmsg_data(nlh);
memset(cfg, 0, sizeof(*cfg));

if (rtm->rtm_family != AF_MPLS)
goto errout;
if (rtm->rtm_dst_len != 20)
goto errout;
if (rtm->rtm_src_len != 0)
goto errout;
if (rtm->rtm_tos != 0)
goto errout;
if (rtm->rtm_table != RT_TABLE_MAIN)
goto errout;
/* Any value is acceptable for rtm_protocol */

/* As mpls uses destination specific addresses
* (or source specific address in the case of multicast)
* all addresses have universal scope.
*/
if (rtm->rtm_scope != RT_SCOPE_UNIVERSE)
goto errout;
if (rtm->rtm_type != RTN_UNICAST)
goto errout;
if (rtm->rtm_flags != 0)
goto errout;

cfg->rc_label = LABEL_NOT_SPECIFIED;
cfg->rc_protocol = rtm->rtm_protocol;
cfg->rc_nlflags = nlh->nlmsg_flags;
cfg->rc_nlinfo.portid = NETLINK_CB(skb).portid;
cfg->rc_nlinfo.nlh = nlh;
cfg->rc_nlinfo.nl_net = sock_net(skb->sk);

for (index = 0; index <= RTA_MAX; index++) {
struct nlattr *nla = tb[index];
if (!nla)
continue;

switch(index) {
case RTA_OIF:
cfg->rc_ifindex = nla_get_u32(nla);
break;
case RTA_NEWDST:
if (nla_get_labels(nla, MAX_NEW_LABELS,
&cfg->rc_output_labels,
cfg->rc_output_label))
goto errout;
break;
case RTA_DST:
{
u32 label_count;
if (nla_get_labels(nla, 1, &label_count,
&cfg->rc_label))
goto errout;

/* The first 16 labels are reserved, and may not be set */
if (cfg->rc_label < 16)
goto errout;

break;
}
case RTA_VIA:
{
struct rtvia *via = nla_data(nla);
cfg->rc_via_family = via->rtvia_family;
cfg->rc_via_alen = nla_len(nla) - 2;
if (cfg->rc_via_alen > MAX_VIA_ALEN)
goto errout;

/* Validate the address family */
switch(cfg->rc_via_family) {
case AF_PACKET:
break;
case AF_INET:
if (cfg->rc_via_alen != 4)
goto errout;
break;
case AF_INET6:
if (cfg->rc_via_alen != 16)
goto errout;
break;
default:
/* Unsupported address family */
goto errout;
}

memcpy(cfg->rc_via, via->rtvia_addr, cfg->rc_via_alen);
break;
}
default:
/* Unsupported attribute */
goto errout;
}
}

err = 0;
errout:
return err;
}

static int mpls_rtm_delroute(struct sk_buff *skb, struct nlmsghdr *nlh)
{
struct mpls_route_config cfg;
int err;

err = rtm_to_route_config(skb, nlh, &cfg);
if (err < 0)
return err;

return mpls_route_del(&cfg);
}


static int mpls_rtm_newroute(struct sk_buff *skb, struct nlmsghdr *nlh)
{
struct mpls_route_config cfg;
int err;

err = rtm_to_route_config(skb, nlh, &cfg);
if (err < 0)
return err;

return mpls_route_add(&cfg);
}

static int mpls_dump_route(struct sk_buff *skb, u32 portid, u32 seq, int event,
u32 label, struct mpls_route *rt, int flags)
{
struct nlmsghdr *nlh;
struct rtmsg *rtm;

nlh = nlmsg_put(skb, portid, seq, event, sizeof(*rtm), flags);
if (nlh == NULL)
return -EMSGSIZE;

rtm = nlmsg_data(nlh);
rtm->rtm_family = AF_MPLS;
rtm->rtm_dst_len = 20;
rtm->rtm_src_len = 0;
rtm->rtm_tos = 0;
rtm->rtm_table = RT_TABLE_MAIN;
rtm->rtm_protocol = rt->rt_protocol;
rtm->rtm_scope = RT_SCOPE_UNIVERSE;
rtm->rtm_type = RTN_UNICAST;
rtm->rtm_flags = 0;

if (rt->rt_labels &&
nla_put_labels(skb, RTA_NEWDST, rt->rt_labels, rt->rt_label))
goto nla_put_failure;
if (nla_put_via(skb, rt->rt_via_family, rt->rt_via, rt->rt_via_alen))
goto nla_put_failure;
if (rt->rt_dev && nla_put_u32(skb, RTA_OIF, rt->rt_dev->ifindex))
goto nla_put_failure;
if (nla_put_labels(skb, RTA_DST, 1, &label))
goto nla_put_failure;

nlmsg_end(skb, nlh);
return 0;

nla_put_failure:
nlmsg_cancel(skb, nlh);
return -EMSGSIZE;
}

static int mpls_dump_routes(struct sk_buff *skb, struct netlink_callback *cb)
{
struct net *net = sock_net(skb->sk);
unsigned int index;

ASSERT_RTNL();

index = cb->args[0];
if (index < 16)
index = 16;

for (; index < net->mpls.platform_labels; index++) {
struct mpls_route *rt;
rt = net->mpls.platform_label[index];
if (!rt)
continue;

if (mpls_dump_route(skb, NETLINK_CB(cb->skb).portid,
cb->nlh->nlmsg_seq, RTM_NEWROUTE,
index, rt, NLM_F_MULTI) < 0)
break;
}
cb->args[0] = index;

return skb->len;
}

static int resize_platform_label_table(struct net *net, size_t limit)
{
size_t size = sizeof(struct mpls_route *) * limit;
Expand Down Expand Up @@ -662,6 +887,9 @@ static int __init mpls_init(void)

dev_add_pack(&mpls_packet_type);

rtnl_register(PF_MPLS, RTM_NEWROUTE, mpls_rtm_newroute, NULL, NULL);
rtnl_register(PF_MPLS, RTM_DELROUTE, mpls_rtm_delroute, NULL, NULL);
rtnl_register(PF_MPLS, RTM_GETROUTE, NULL, mpls_dump_routes, NULL);
err = 0;
out:
return err;
Expand All @@ -674,6 +902,7 @@ module_init(mpls_init);

static void __exit mpls_exit(void)
{
rtnl_unregister_all(PF_MPLS);
dev_remove_pack(&mpls_packet_type);
unregister_netdevice_notifier(&mpls_dev_notifier);
unregister_pernet_subsys(&mpls_net_ops);
Expand Down

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