From: Lennart Poettering <lennart@poettering.net>
Date: Thu, 2 Nov 2023 10:31:13 +0000 (+0100)
Subject: fd-util: add new FORMAT_PROC_PID_FD_PATH() helper
X-Git-Tag: v255-rc1~43^2~11
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=61c062f896a9a59cab6899d3c8ba3e3d1e4e0c61;p=thirdparty%2Fsystemd.git

fd-util: add new FORMAT_PROC_PID_FD_PATH() helper

This is just like FORMAT_PROC_FD_PATH() but goes via the PID number
rather than the "self" symlink.

This is useful whenever we want to generate a path that is useful
outside of our local scope.
---

diff --git a/src/basic/fd-util.c b/src/basic/fd-util.c
index f2b606ea9b4..32289cfd09e 100644
--- a/src/basic/fd-util.c
+++ b/src/basic/fd-util.c
@@ -988,3 +988,11 @@ const char *accmode_to_string(int flags) {
                 return NULL;
         }
 }
+
+char *format_proc_pid_fd_path(char buf[static PROC_PID_FD_PATH_MAX], pid_t pid, int fd) {
+        assert(buf);
+        assert(fd >= 0);
+        assert(pid >= 0);
+        assert_se(snprintf_ok(buf, PROC_PID_FD_PATH_MAX, "/proc/" PID_FMT "/fd/%i", pid == 0 ? getpid_cached() : pid, fd));
+        return buf;
+}
diff --git a/src/basic/fd-util.h b/src/basic/fd-util.h
index aba8f5f5af9..5061e32196a 100644
--- a/src/basic/fd-util.h
+++ b/src/basic/fd-util.h
@@ -131,6 +131,16 @@ static inline char *format_proc_fd_path(char buf[static PROC_FD_PATH_MAX], int f
 #define FORMAT_PROC_FD_PATH(fd) \
         format_proc_fd_path((char[PROC_FD_PATH_MAX]) {}, (fd))
 
+/* The maximum length a buffer for a /proc/<pid>/fd/<fd> path needs */
+#define PROC_PID_FD_PATH_MAX \
+        (STRLEN("/proc//fd/") + DECIMAL_STR_MAX(pid_t) + DECIMAL_STR_MAX(int))
+
+char *format_proc_pid_fd_path(char buf[static PROC_PID_FD_PATH_MAX], pid_t pid, int fd);
+
+/* Kinda the same as FORMAT_PROC_FD_PATH(), but goes by PID rather than "self" symlink */
+#define FORMAT_PROC_PID_FD_PATH(pid, fd)                                \
+        format_proc_pid_fd_path((char[PROC_PID_FD_PATH_MAX]) {}, (pid), (fd))
+
 const char *accmode_to_string(int flags);
 
 /* Like ASSERT_PTR, but for fds */