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Subject[RFC V2 PATCH 21/25] net/netpolicy: set per task policy by proc
Date
From: Kan Liang <kan.liang@intel.com>

Users may not want to change the source code to add per task net polic
support. Or they may want to change a running task's net policy. prctl
does not work for both cases.

This patch adds an interface in /proc, which can be used to set and
retrieve policy of already running tasks. User can write the policy name
into /proc/$PID/net_policy to set per task net policy.

Signed-off-by: Kan Liang <kan.liang@intel.com>
---
fs/proc/base.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 64 insertions(+)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index a11eb71..7679785 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -91,6 +91,8 @@
#include <asm/hardwall.h>
#endif
#include <trace/events/oom.h>
+#include <linux/netpolicy.h>
+#include <linux/ctype.h>
#include "internal.h"
#include "fd.h"

@@ -2807,6 +2809,65 @@ static int proc_pid_personality(struct seq_file *m, struct pid_namespace *ns,
return err;
}

+#ifdef CONFIG_NETPOLICY
+static int proc_net_policy_show(struct seq_file *m, void *v)
+{
+ struct inode *inode = m->private;
+ struct task_struct *task = get_proc_task(inode);
+
+ if (is_net_policy_valid(task->task_netpolicy.policy))
+ seq_printf(m, "%s\n", policy_name[task->task_netpolicy.policy]);
+
+ return 0;
+}
+
+static int proc_net_policy_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, proc_net_policy_show, inode);
+}
+
+static ssize_t proc_net_policy_write(struct file *file, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ struct inode *inode = file_inode(file);
+ struct task_struct *task = get_proc_task(inode);
+ char name[POLICY_NAME_LEN_MAX];
+ int i, ret;
+
+ if (count >= POLICY_NAME_LEN_MAX)
+ return -EINVAL;
+
+ if (copy_from_user(name, buf, count))
+ return -EINVAL;
+
+ for (i = 0; i < count - 1; i++)
+ name[i] = toupper(name[i]);
+ name[POLICY_NAME_LEN_MAX - 1] = 0;
+
+ for (i = 0; i < NET_POLICY_MAX; i++) {
+ if (!strncmp(name, policy_name[i], strlen(policy_name[i]))) {
+ ret = netpolicy_register(&task->task_netpolicy, i);
+ if (ret)
+ return ret;
+ break;
+ }
+ }
+
+ if (i == NET_POLICY_MAX)
+ return -EINVAL;
+
+ return count;
+}
+
+static const struct file_operations proc_net_policy_operations = {
+ .open = proc_net_policy_open,
+ .write = proc_net_policy_write,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+#endif /* CONFIG_NETPOLICY */
+
/*
* Thread groups
*/
@@ -2906,6 +2967,9 @@ static const struct pid_entry tgid_base_stuff[] = {
REG("timers", S_IRUGO, proc_timers_operations),
#endif
REG("timerslack_ns", S_IRUGO|S_IWUGO, proc_pid_set_timerslack_ns_operations),
+#if IS_ENABLED(CONFIG_NETPOLICY)
+ REG("net_policy", S_IRUSR|S_IWUSR, proc_net_policy_operations),
+#endif
};

static int proc_tgid_base_readdir(struct file *file, struct dir_context *ctx)
--
2.5.5
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