[PATCH 13/24] man/man7/sock_diag.7: Document UDIAG_SHOW_UID

["Günther Noack" <gnoack3000@gmail.com>]

linux.git cae9910e7344 ("net: Add UNIX_DIAG_UID to Netlink UNIX socket
diagnostics."), first released in Linux 5.3, added the UDIAG_SHOW_UID
flag and the UNIX_DIAG_UID attribute.  sk_diag_dump_uid() in
net/unix/diag.c reports sk_uid(sk) as a uid_t, mapped with
from_kuid_munged() into the user namespace of the requesting netlink
socket.

Assisted-by: LLM
Cc: Felipe Gasper <felipe@felipegasper.com>
Signed-off-by: Günther Noack <gnoack3000@gmail.com>
---

Notes:
    This documents a missing sock_diag feature introduced in 2019.
    
    The phrasing mirrors the phrasing of adjacent sections about other
    features.

 man/man7/sock_diag.7 | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/man/man7/sock_diag.7 b/man/man7/sock_diag.7
index 9a2b54a67b30..c82b24fe1198 100644
--- a/man/man7/sock_diag.7
+++ b/man/man7/sock_diag.7
@@ -265,6 +265,16 @@ The attribute reported in answer to this request is
 .BR UNIX_DIAG_MEMINFO .
 The payload associated with this attribute is an array of __u32 values
 described below in the subsection "Socket memory information".
+.TP
+.BR UDIAG_SHOW_UID " (since Linux 5.3)"
+.\" commit cae9910e73446cac68a54e3a7b02aaa12b689026
+The attribute reported in answer to this request is
+.BR UNIX_DIAG_UID .
+The payload associated with this attribute is a
+.I uid_t
+value which is the user ID of the owner of the socket,
+as seen from the user namespace of the netlink socket
+that is used for the query.
 .P
 The following attributes are reported back without any specific request:
 .TP
-- 
2.56.0