net: core: Support UID-based routing.

This contains the following commits:

1. cc2f522 net: core: Add a UID range to fib rules.
2. d7ed2bd net: core: Use the socket UID in routing lookups.
3. 2f9306a net: core: Add a RTA_UID attribute to routes.
    This is so that userspace can do per-UID route lookups.
4. 8e46efb net: ipv6: Use the UID in IPv6 PMTUD
    IPv4 PMTUD already does this because ipv4_sk_update_pmtu
    uses __build_flow_key, which includes the UID.

Bug: 15413527
Change-Id: I81bd31dae655de9cce7d7a1f9a905dc1c2feba7c
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>

1 files changed, 51 insertions, 2 deletions

diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index 0e9131195eb..a40a876b855 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -31,6 +31,8 @@ int fib_default_rule_add(struct fib_rules_ops *ops,
 	r->pref = pref;
 	r->table = table;
 	r->flags = flags;
+	r->uid_start = INVALID_UID;
+	r->uid_end = INVALID_UID;
 	r->fr_net = hold_net(ops->fro_net);
 
 	/* The lock is not required here, the list in unreacheable
@@ -179,6 +181,23 @@ void fib_rules_unregister(struct fib_rules_ops *ops)
 }
 EXPORT_SYMBOL_GPL(fib_rules_unregister);
 
+static inline kuid_t fib_nl_uid(struct nlattr *nla)
+{
+	return make_kuid(current_user_ns(), nla_get_u32(nla));
+}
+
+static int nla_put_uid(struct sk_buff *skb, int idx, kuid_t uid)
+{
+	return nla_put_u32(skb, idx, from_kuid_munged(current_user_ns(), uid));
+}
+
+static int fib_uid_range_match(struct flowi *fl, struct fib_rule *rule)
+{
+	return (!uid_valid(rule->uid_start) && !uid_valid(rule->uid_end)) ||
+	       (uid_gte(fl->flowi_uid, rule->uid_start) &&
+		uid_lte(fl->flowi_uid, rule->uid_end));
+}
+
 static int fib_rule_match(struct fib_rule *rule, struct fib_rules_ops *ops,
 			  struct flowi *fl, int flags)
 {
@@ -193,6 +212,9 @@ static int fib_rule_match(struct fib_rule *rule, struct fib_rules_ops *ops,
 	if ((rule->mark ^ fl->flowi_mark) & rule->mark_mask)
 		goto out;
 
+	if (!fib_uid_range_match(fl, rule))
+		goto out;
+
 	ret = ops->match(rule, fl, flags);
 out:
 	return (rule->flags & FIB_RULE_INVERT) ? !ret : ret;
@@ -363,6 +385,19 @@ static int fib_nl_newrule(struct sk_buff *skb, struct nlmsghdr* nlh)
 	} else if (rule->action == FR_ACT_GOTO)
 		goto errout_free;
 
+	/* UID start and end must either both be valid or both unspecified. */
+	rule->uid_start = rule->uid_end = INVALID_UID;
+	if (tb[FRA_UID_START] || tb[FRA_UID_END]) {
+		if (tb[FRA_UID_START] && tb[FRA_UID_END]) {
+			rule->uid_start = fib_nl_uid(tb[FRA_UID_START]);
+			rule->uid_end = fib_nl_uid(tb[FRA_UID_END]);
+		}
+		if (!uid_valid(rule->uid_start) ||
+		    !uid_valid(rule->uid_end) ||
+		    !uid_lte(rule->uid_start, rule->uid_end))
+		goto errout_free;
+	}
+
 	err = ops->configure(rule, skb, frh, tb);
 	if (err < 0)
 		goto errout_free;
@@ -469,6 +504,14 @@ static int fib_nl_delrule(struct sk_buff *skb, struct nlmsghdr* nlh)
 		    (rule->mark_mask != nla_get_u32(tb[FRA_FWMASK])))
 			continue;
 
+		if (tb[FRA_UID_START] &&
+		    !uid_eq(rule->uid_start, fib_nl_uid(tb[FRA_UID_START])))
+			continue;
+
+		if (tb[FRA_UID_END] &&
+		    !uid_eq(rule->uid_end, fib_nl_uid(tb[FRA_UID_END])))
+			continue;
+
 		if (!ops->compare(rule, frh, tb))
 			continue;
 
@@ -525,7 +568,9 @@ static inline size_t fib_rule_nlmsg_size(struct fib_rules_ops *ops,
 			 + nla_total_size(4) /* FRA_PRIORITY */
 			 + nla_total_size(4) /* FRA_TABLE */
 			 + nla_total_size(4) /* FRA_FWMARK */
-			 + nla_total_size(4); /* FRA_FWMASK */
+			 + nla_total_size(4) /* FRA_FWMASK */
+			 + nla_total_size(4) /* FRA_UID_START */
+			 + nla_total_size(4); /* FRA_UID_END */
 
 	if (ops->nlmsg_payload)
 		payload += ops->nlmsg_payload(rule);
@@ -579,7 +624,11 @@ static int fib_nl_fill_rule(struct sk_buff *skb, struct fib_rule *rule,
 	    ((rule->mark_mask || rule->mark) &&
 	     nla_put_u32(skb, FRA_FWMASK, rule->mark_mask)) ||
 	    (rule->target &&
-	     nla_put_u32(skb, FRA_GOTO, rule->target)))
+	     nla_put_u32(skb, FRA_GOTO, rule->target)) ||
+	    (uid_valid(rule->uid_start) &&
+	     nla_put_uid(skb, FRA_UID_START, rule->uid_start)) ||
+	    (uid_valid(rule->uid_end) &&
+	     nla_put_uid(skb, FRA_UID_END, rule->uid_end)))
 		goto nla_put_failure;
 	if (ops->fill(rule, skb, frh) < 0)
 		goto nla_put_failure;