Subject: [PATCH iproute2-next 1/4] namespace: Add function to return fd for netns by pid

From: David Ahern <[email-masked]>
Date: Thu, 7 May 2026 09:08:32 -0600

From: David Ahern <[email-masked]>

Add netns_get_fd_pid - verifies string is an integer,
then returns an fd to /proc/$pid/ns/net.

Signed-off-by: David Ahern <[email-masked]>
---
 include/namespace.h |  1 +
 lib/namespace.c     | 13 +++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/include/namespace.h b/include/namespace.h
index 98f4af59..6a6fa438 100644
--- a/include/namespace.h
+++ b/include/namespace.h
@@ -52,6 +52,7 @@ static inline int setns(int fd, int nstype)
 
 int netns_switch(char *netns);
 int netns_get_fd(const char *netns);
+int netns_get_fd_pid(const char *pidstr);
 int netns_foreach(int (*func)(char *nsname, void *arg), void *arg);
 
 struct netns_func {
diff --git a/lib/namespace.c b/lib/namespace.c
index 74b7e7ca..f391c694 100644
--- a/lib/namespace.c
+++ b/lib/namespace.c
@@ -114,6 +114,19 @@ int netns_get_fd(const char *name)
 	return open(path, O_RDONLY);
 }
 
+int netns_get_fd_pid(const char *pidstr)
+{
+	char path[PATH_MAX];
+	int pid;
+
+	/* make sure it is an integer */
+	if (get_integer(&pid, pidstr, 0) < 0)
+		return -1;
+
+	snprintf(path, sizeof(path), "/proc/%s/ns/net", pidstr);
+	return open(path, O_RDONLY);
+}
+
 int netns_foreach(int (*func)(char *nsname, void *arg), void *arg)
 {
 	DIR *dir;
-- 
2.50.1 (Apple Git-155)