From da5e0c442bc1f0e1e47ab92b0196e99e7c4ffafd Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Thu, 23 Nov 2023 17:58:01 +0100
Subject: [PATCH] socket-util: add helper for getting peer pidfd

---
 src/basic/missing_socket.h |  4 ++++
 src/basic/socket-util.c    | 15 +++++++++++++++
 src/basic/socket-util.h    |  1 +
 3 files changed, 20 insertions(+)

diff --git a/src/basic/missing_socket.h b/src/basic/missing_socket.h
index 30ac297e171..3333cf18e7a 100644
--- a/src/basic/missing_socket.h
+++ b/src/basic/missing_socket.h
@@ -32,6 +32,10 @@ struct sockaddr_vm {
 #define SO_PEERGROUPS 59
 #endif
 
+#ifndef SO_PEERPIDFD
+#define SO_PEERPIDFD 77
+#endif
+
 #ifndef SO_BINDTOIFINDEX
 #define SO_BINDTOIFINDEX 62
 #endif
diff --git a/src/basic/socket-util.c b/src/basic/socket-util.c
index 86472c88474..98133a2ecda 100644
--- a/src/basic/socket-util.c
+++ b/src/basic/socket-util.c
@@ -956,6 +956,21 @@ int getpeergroups(int fd, gid_t **ret) {
         return (int) n;
 }
 
+int getpeerpidfd(int fd) {
+        socklen_t n = sizeof(int);
+        int pidfd = -EBADF;
+
+        assert(fd >= 0);
+
+        if (getsockopt(fd, SOL_SOCKET, SO_PEERPIDFD, &pidfd, &n) < 0)
+                return -errno;
+
+        if (n != sizeof(int))
+                return -EIO;
+
+        return pidfd;
+}
+
 ssize_t send_many_fds_iov_sa(
                 int transport_fd,
                 int *fds_array, size_t n_fds_array,
diff --git a/src/basic/socket-util.h b/src/basic/socket-util.h
index 9a11df834d1..032d73857ed 100644
--- a/src/basic/socket-util.h
+++ b/src/basic/socket-util.h
@@ -152,6 +152,7 @@ bool address_label_valid(const char *p);
 int getpeercred(int fd, struct ucred *ucred);
 int getpeersec(int fd, char **ret);
 int getpeergroups(int fd, gid_t **ret);
+int getpeerpidfd(int fd);
 
 ssize_t send_many_fds_iov_sa(
                 int transport_fd,