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ipv4: Allow ipv6 gateway with ipv4 routes
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Add support for RTA_VIA and allow an IPv6 nexthop for v4 routes:
   $ ip ro add 172.16.1.0/24 via inet6 2001:db8::1 dev eth0
   $ ip ro ls
   ...
   172.16.1.0/24 via inet6 2001:db8::1 dev eth0

For convenience and simplicity, userspace can use RTA_VIA to specify
AF_INET or AF_INET6 gateway.

The common fib_nexthop_info dump function compares the gateway address
family to the nh_common family to know if the gateway should be encoded
as RTA_VIA or RTA_GATEWAY.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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David Ahern authored and David S. Miller committed Apr 8, 2019
1 parent 19a9d13 commit d156626
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Showing 3 changed files with 123 additions and 8 deletions.
2 changes: 2 additions & 0 deletions include/net/ip_fib.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -401,6 +401,8 @@ static inline bool fib4_rules_early_flow_dissect(struct net *net,
/* Exported by fib_frontend.c */
extern const struct nla_policy rtm_ipv4_policy[];
void ip_fib_init(void);
int fib_gw_from_via(struct fib_config *cfg, struct nlattr *nla,
struct netlink_ext_ack *extack);
__be32 fib_compute_spec_dst(struct sk_buff *skb);
bool fib_info_nh_uses_dev(struct fib_info *fi, const struct net_device *dev);
int fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst,
Expand Down
60 changes: 57 additions & 3 deletions net/ipv4/fib_frontend.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -665,10 +665,55 @@ const struct nla_policy rtm_ipv4_policy[RTA_MAX + 1] = {
[RTA_DPORT] = { .type = NLA_U16 },
};

int fib_gw_from_via(struct fib_config *cfg, struct nlattr *nla,
struct netlink_ext_ack *extack)
{
struct rtvia *via;
int alen;

if (nla_len(nla) < offsetof(struct rtvia, rtvia_addr)) {
NL_SET_ERR_MSG(extack, "Invalid attribute length for RTA_VIA");
return -EINVAL;
}

via = nla_data(nla);
alen = nla_len(nla) - offsetof(struct rtvia, rtvia_addr);

switch (via->rtvia_family) {
case AF_INET:
if (alen != sizeof(__be32)) {
NL_SET_ERR_MSG(extack, "Invalid IPv4 address in RTA_VIA");
return -EINVAL;
}
cfg->fc_gw_family = AF_INET;
cfg->fc_gw4 = *((__be32 *)via->rtvia_addr);
break;
case AF_INET6:
#ifdef CONFIG_IPV6
if (alen != sizeof(struct in6_addr)) {
NL_SET_ERR_MSG(extack, "Invalid IPv6 address in RTA_VIA");
return -EINVAL;
}
cfg->fc_gw_family = AF_INET6;
cfg->fc_gw6 = *((struct in6_addr *)via->rtvia_addr);
#else
NL_SET_ERR_MSG(extack, "IPv6 support not enabled in kernel");
return -EINVAL;
#endif
break;
default:
NL_SET_ERR_MSG(extack, "Unsupported address family in RTA_VIA");
return -EINVAL;
}

return 0;
}

static int rtm_to_fib_config(struct net *net, struct sk_buff *skb,
struct nlmsghdr *nlh, struct fib_config *cfg,
struct netlink_ext_ack *extack)
{
bool has_gw = false, has_via = false;
struct nlattr *attr;
int err, remaining;
struct rtmsg *rtm;
Expand Down Expand Up @@ -709,13 +754,16 @@ static int rtm_to_fib_config(struct net *net, struct sk_buff *skb,
cfg->fc_oif = nla_get_u32(attr);
break;
case RTA_GATEWAY:
has_gw = true;
cfg->fc_gw_family = AF_INET;
cfg->fc_gw4 = nla_get_be32(attr);
break;
case RTA_VIA:
NL_SET_ERR_MSG(extack, "IPv4 does not support RTA_VIA attribute");
err = -EINVAL;
goto errout;
has_via = true;
err = fib_gw_from_via(cfg, attr, extack);
if (err)
goto errout;
break;
case RTA_PRIORITY:
cfg->fc_priority = nla_get_u32(attr);
break;
Expand Down Expand Up @@ -754,6 +802,12 @@ static int rtm_to_fib_config(struct net *net, struct sk_buff *skb,
}
}

if (has_gw && has_via) {
NL_SET_ERR_MSG(extack,
"Nexthop configuration can not contain both GATEWAY and VIA");
goto errout;
}

return 0;
errout:
return err;
Expand Down
69 changes: 64 additions & 5 deletions net/ipv4/fib_semantics.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -606,12 +606,22 @@ static int fib_get_nhs(struct fib_info *fi, struct rtnexthop *rtnh,

attrlen = rtnh_attrlen(rtnh);
if (attrlen > 0) {
struct nlattr *nla, *attrs = rtnh_attrs(rtnh);
struct nlattr *nla, *nlav, *attrs = rtnh_attrs(rtnh);

nla = nla_find(attrs, attrlen, RTA_GATEWAY);
nlav = nla_find(attrs, attrlen, RTA_VIA);
if (nla && nlav) {
NL_SET_ERR_MSG(extack,
"Nexthop configuration can not contain both GATEWAY and VIA");
return -EINVAL;
}
if (nla) {
fib_cfg.fc_gw_family = AF_INET;
fib_cfg.fc_gw4 = nla_get_in_addr(nla);
} else if (nlav) {
ret = fib_gw_from_via(&fib_cfg, nlav, extack);
if (ret)
goto errout;
}

nla = nla_find(attrs, attrlen, RTA_FLOW);
Expand Down Expand Up @@ -792,11 +802,43 @@ int fib_nh_match(struct fib_config *cfg, struct fib_info *fi,

attrlen = rtnh_attrlen(rtnh);
if (attrlen > 0) {
struct nlattr *nla, *attrs = rtnh_attrs(rtnh);
struct nlattr *nla, *nlav, *attrs = rtnh_attrs(rtnh);

nla = nla_find(attrs, attrlen, RTA_GATEWAY);
if (nla && nla_get_in_addr(nla) != nh->fib_nh_gw4)
return 1;
nlav = nla_find(attrs, attrlen, RTA_VIA);
if (nla && nlav) {
NL_SET_ERR_MSG(extack,
"Nexthop configuration can not contain both GATEWAY and VIA");
return -EINVAL;
}

if (nla) {
if (nh->fib_nh_gw_family != AF_INET ||
nla_get_in_addr(nla) != nh->fib_nh_gw4)
return 1;
} else if (nlav) {
struct fib_config cfg2;
int err;

err = fib_gw_from_via(&cfg2, nlav, extack);
if (err)
return err;

switch (nh->fib_nh_gw_family) {
case AF_INET:
if (cfg2.fc_gw_family != AF_INET ||
cfg2.fc_gw4 != nh->fib_nh_gw4)
return 1;
break;
case AF_INET6:
if (cfg2.fc_gw_family != AF_INET6 ||
ipv6_addr_cmp(&cfg2.fc_gw6,
&nh->fib_nh_gw6))
return 1;
break;
}
}

#ifdef CONFIG_IP_ROUTE_CLASSID
nla = nla_find(attrs, attrlen, RTA_FLOW);
if (nla && nla_get_u32(nla) != nh->nh_tclassid)
Expand Down Expand Up @@ -1429,8 +1471,25 @@ int fib_nexthop_info(struct sk_buff *skb, const struct fib_nh_common *nhc,
goto nla_put_failure;
break;
case AF_INET6:
if (nla_put_in6_addr(skb, RTA_GATEWAY, &nhc->nhc_gw.ipv6) < 0)
/* if gateway family does not match nexthop family
* gateway is encoded as RTA_VIA
*/
if (nhc->nhc_gw_family != nhc->nhc_family) {
int alen = sizeof(struct in6_addr);
struct nlattr *nla;
struct rtvia *via;

nla = nla_reserve(skb, RTA_VIA, alen + 2);
if (!nla)
goto nla_put_failure;

via = nla_data(nla);
via->rtvia_family = AF_INET6;
memcpy(via->rtvia_addr, &nhc->nhc_gw.ipv6, alen);
} else if (nla_put_in6_addr(skb, RTA_GATEWAY,
&nhc->nhc_gw.ipv6) < 0) {
goto nla_put_failure;
}
break;
}

Expand Down

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