socket-util: introduce getpeerpidref()

This combines getpeercred() and getpeerpidfd() and returns a PidRef

src/basic/socket-util.c

@@ -975,6 +975,28 @@ int getpeerpidfd(int fd) {
         return pidfd;
 }
 
+int getpeerpidref(int fd, PidRef *ret) {
+        int r;
+
+        assert(fd >= 0);
+        assert(ret);
+
+        int pidfd = getpeerpidfd(fd);
+        if (pidfd < 0) {
+                if (!ERRNO_IS_NEG_NOT_SUPPORTED(pidfd))
+                        return pidfd;
+
+                struct ucred ucred;
+                r = getpeercred(fd, &ucred);
+                if (r < 0)
+                        return r;
+
+                return pidref_set_pid(ret, ucred.pid);
+        }
+
+        return pidref_set_pidfd_consume(ret, pidfd);
+}
+
 ssize_t send_many_fds_iov_sa(
                 int transport_fd,
                 int *fds_array, size_t n_fds_array,

src/basic/socket-util.h

@@ -20,6 +20,7 @@
 #include "macro.h"
 #include "missing_network.h"
 #include "missing_socket.h"
+#include "pidref.h"
 #include "sparse-endian.h"
 
 union sockaddr_union {
@@ -154,6 +155,7 @@ int getpeercred(int fd, struct ucred *ucred);
 int getpeersec(int fd, char **ret);
 int getpeergroups(int fd, gid_t **ret);
 int getpeerpidfd(int fd);
+int getpeerpidref(int fd, PidRef *ret);
 
 ssize_t send_many_fds_iov_sa(
                 int transport_fd,

src/test/test-socket-util.c

@@ -584,4 +584,25 @@ TEST(sockaddr_un_set_path) {
         assert_se(connect(fd2, &sa.sa, SOCKADDR_LEN(sa)) >= 0);
 }
 
+TEST(getpeerpidref) {
+        _cleanup_close_pair_ int fd[2] = EBADF_PAIR;
+
+        ASSERT_OK(socketpair(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0, fd));
+
+        _cleanup_(pidref_done) PidRef pidref0 = PIDREF_NULL, pidref1 = PIDREF_NULL, pidref_self = PIDREF_NULL, pidref_pid1 = PIDREF_NULL;
+        ASSERT_OK(getpeerpidref(fd[0], &pidref0));
+        ASSERT_OK(getpeerpidref(fd[1], &pidref1));
+
+        ASSERT_OK(pidref_set_self(&pidref_self));
+        ASSERT_OK(pidref_set_pid(&pidref_pid1, 1));
+
+        ASSERT_TRUE(pidref_equal(&pidref0, &pidref1));
+        ASSERT_TRUE(pidref_equal(&pidref0, &pidref_self));
+        ASSERT_TRUE(pidref_equal(&pidref1, &pidref_self));
+
+        ASSERT_TRUE(!pidref_equal(&pidref_self, &pidref_pid1));
+        ASSERT_TRUE(!pidref_equal(&pidref1, &pidref_pid1));
+        ASSERT_TRUE(!pidref_equal(&pidref0, &pidref_pid1));
+}
+
 DEFINE_TEST_MAIN(LOG_DEBUG);