[PATCH 1/1] [RFC] sunrpc: inject process namespace into machinename field

On large shared machines often multiple jobs of a same user run in
parallel. For debugging, it's usually impossible to identify requests
coming from different processes.

The batch systems like HTCondor or SLURM start every job in it's own
namespace, thus passing namespace info to the server will help by
debugging.

Signed-off-by: Tigran Mkrtchyan <[email protected]>
---
 net/sunrpc/auth_unix.c | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/net/sunrpc/auth_unix.c b/net/sunrpc/auth_unix.c
index 6c742a3400c4..b218cfa9871a 100644
--- a/net/sunrpc/auth_unix.c
+++ b/net/sunrpc/auth_unix.c
@@ -15,6 +15,7 @@
 #include <linux/sunrpc/clnt.h>
 #include <linux/sunrpc/auth.h>
 #include <linux/user_namespace.h>
+#include <linux/pid_namespace.h>
 
 
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
@@ -117,6 +118,28 @@ unx_marshal(struct rpc_task *task, struct xdr_stream *xdr)
 	struct group_info *gi = cred->cr_cred->group_info;
 	struct user_namespace *userns = clnt->cl_cred ?
 		clnt->cl_cred->user_ns : &init_user_ns;
+	char ns_aware_nodename[UNX_MAXNODENAME + 1];
+	int ns_aware_nodename_len;
+
+	struct pid_namespace *pid_ns = task_active_pid_ns(current);
+
+	/* the process runs in a dedicated namespace */
+	if (pid_ns != &init_pid_ns) {
+		/* Format as: <pid_ns_inum>@<current-hostname> */
+		int prefix_len = snprintf(ns_aware_nodename, sizeof(ns_aware_nodename),
+			"%u@", pid_ns->ns.inum);
+
+		if (prefix_len < sizeof(ns_aware_nodename))
+			strscpy(ns_aware_nodename + prefix_len, clnt->cl_nodename,
+				sizeof(ns_aware_nodename) - prefix_len);
+		else
+			strscpy(ns_aware_nodename, clnt->cl_nodename, sizeof(ns_aware_nodename));
+
+		ns_aware_nodename_len = strlen(ns_aware_nodename);
+	} else {
+		ns_aware_nodename_len = clnt->cl_nodelen;
+		strscpy(ns_aware_nodename, clnt->cl_nodename, sizeof(ns_aware_nodename));
+	}
 
 	/* Credential */
 
@@ -126,8 +149,8 @@ unx_marshal(struct rpc_task *task, struct xdr_stream *xdr)
 	*p++ = rpc_auth_unix;
 	cred_len = p++;
 	*p++ = xdr_zero;	/* stamp */
-	if (xdr_stream_encode_opaque(xdr, clnt->cl_nodename,
-				     clnt->cl_nodelen) < 0)
+	if (xdr_stream_encode_opaque(xdr, ns_aware_nodename,
+				     ns_aware_nodename_len) < 0)
 		goto marshal_failed;
 	p = xdr_reserve_space(xdr, 3 * sizeof(*p));
 	if (!p)
-- 
2.54.0