[TCP]: Restrict congestion control choices.
Allow normal users to only choose among a restricted set of congestion
control choices. The default is reno and what ever has been configured
as default. But the policy can be changed by administrator at any time.
For example, to allow any choice:
cp /proc/sys/net/ipv4/tcp_available_congestion_control \
/proc/sys/net/ipv4/tcp_allowed_congestion_control
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 2e770f4..dfcf47f 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -146,6 +146,50 @@
return ret;
}
+static int proc_allowed_congestion_control(ctl_table *ctl,
+ int write, struct file * filp,
+ void __user *buffer, size_t *lenp,
+ loff_t *ppos)
+{
+ ctl_table tbl = { .maxlen = TCP_CA_BUF_MAX };
+ int ret;
+
+ tbl.data = kmalloc(tbl.maxlen, GFP_USER);
+ if (!tbl.data)
+ return -ENOMEM;
+
+ tcp_get_allowed_congestion_control(tbl.data, tbl.maxlen);
+ ret = proc_dostring(&tbl, write, filp, buffer, lenp, ppos);
+ if (write && ret == 0)
+ ret = tcp_set_allowed_congestion_control(tbl.data);
+ kfree(tbl.data);
+ return ret;
+}
+
+static int strategy_allowed_congestion_control(ctl_table *table, int __user *name,
+ int nlen, void __user *oldval,
+ size_t __user *oldlenp,
+ void __user *newval, size_t newlen,
+ void **context)
+{
+ ctl_table tbl = { .maxlen = TCP_CA_BUF_MAX };
+ int ret;
+
+ tbl.data = kmalloc(tbl.maxlen, GFP_USER);
+ if (!tbl.data)
+ return -ENOMEM;
+
+ tcp_get_available_congestion_control(tbl.data, tbl.maxlen);
+ ret = sysctl_string(&tbl, name, nlen, oldval, oldlenp, newval, newlen,
+ context);
+ if (ret == 0 && newval && newlen)
+ ret = tcp_set_allowed_congestion_control(tbl.data);
+ kfree(tbl.data);
+
+ return ret;
+
+}
+
ctl_table ipv4_table[] = {
{
.ctl_name = NET_IPV4_TCP_TIMESTAMPS,
@@ -755,6 +799,14 @@
.mode = 0444,
.proc_handler = &proc_tcp_available_congestion_control,
},
+ {
+ .ctl_name = NET_TCP_ALLOWED_CONG_CONTROL,
+ .procname = "tcp_allowed_congestion_control",
+ .maxlen = TCP_CA_BUF_MAX,
+ .mode = 0644,
+ .proc_handler = &proc_allowed_congestion_control,
+ .strategy = &strategy_allowed_congestion_control,
+ },
{ .ctl_name = 0 }
};
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index d846d7b..343d619 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -123,6 +123,7 @@
#endif
if (ca) {
+ ca->non_restricted = 1; /* default is always allowed */
list_move(&ca->list, &tcp_cong_list);
ret = 0;
}
@@ -168,6 +169,64 @@
rcu_read_unlock();
}
+/* Built list of non-restricted congestion control values */
+void tcp_get_allowed_congestion_control(char *buf, size_t maxlen)
+{
+ struct tcp_congestion_ops *ca;
+ size_t offs = 0;
+
+ *buf = '\0';
+ rcu_read_lock();
+ list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
+ if (!ca->non_restricted)
+ continue;
+ offs += snprintf(buf + offs, maxlen - offs,
+ "%s%s",
+ offs == 0 ? "" : " ", ca->name);
+
+ }
+ rcu_read_unlock();
+}
+
+/* Change list of non-restricted congestion control */
+int tcp_set_allowed_congestion_control(char *val)
+{
+ struct tcp_congestion_ops *ca;
+ char *clone, *name;
+ int ret = 0;
+
+ clone = kstrdup(val, GFP_USER);
+ if (!clone)
+ return -ENOMEM;
+
+ spin_lock(&tcp_cong_list_lock);
+ /* pass 1 check for bad entries */
+ while ((name = strsep(&clone, " ")) && *name) {
+ ca = tcp_ca_find(name);
+ if (!ca) {
+ ret = -ENOENT;
+ goto out;
+ }
+ }
+
+ /* pass 2 clear */
+ list_for_each_entry_rcu(ca, &tcp_cong_list, list)
+ ca->non_restricted = 0;
+
+ /* pass 3 mark as allowed */
+ while ((name = strsep(&val, " ")) && *name) {
+ ca = tcp_ca_find(name);
+ WARN_ON(!ca);
+ if (ca)
+ ca->non_restricted = 1;
+ }
+out:
+ spin_unlock(&tcp_cong_list_lock);
+
+ return ret;
+}
+
+
/* Change congestion control for socket */
int tcp_set_congestion_control(struct sock *sk, const char *name)
{
@@ -183,6 +242,9 @@
if (!ca)
err = -ENOENT;
+ else if (!(ca->non_restricted || capable(CAP_NET_ADMIN)))
+ err = -EPERM;
+
else if (!try_module_get(ca->owner))
err = -EBUSY;
@@ -284,6 +346,7 @@
struct tcp_congestion_ops tcp_reno = {
.name = "reno",
+ .non_restricted = 1,
.owner = THIS_MODULE,
.ssthresh = tcp_reno_ssthresh,
.cong_avoid = tcp_reno_cong_avoid,