seitan: separate function in common

Move find_fd_seccomp_notifier to common.c to be reused
in other places.

Signed-off-by: Alice Frosi <afrosi@redhat.com>

1 files changed, 51 insertions, 0 deletions

diff --git a/common.c b/common.c
new file mode 100644
index 0000000..a8f79a2
--- /dev/null
+++ b/common.c
@@ -0,0 +1,51 @@
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+#include <dirent.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+
+int find_fd_seccomp_notifier(const char *path)
+{
+	char entry[2 * PATH_MAX + 1];
+	char buf[PATH_MAX + 1];
+	struct dirent *dp;
+	ssize_t nbytes;
+	struct stat sb;
+	DIR *dirp;
+
+	if ((dirp = opendir(path)) == NULL) {
+		fprintf(stderr, "failed reading fds from proc: %s \n", path);
+		return -1;
+	}
+	while ((dp = readdir(dirp)) != NULL) {
+		snprintf(entry, sizeof(entry), "%s/%s", path, dp->d_name);
+		if (lstat(entry, &sb) == -1) {
+			perror("lstat");
+		}
+		/* Skip the entry if it isn't a symbolic link */
+		if (!S_ISLNK(sb.st_mode))
+			continue;
+
+		nbytes = readlink(entry, buf, PATH_MAX);
+		if (nbytes == -1) {
+			perror("readlink");
+		}
+		if (nbytes == PATH_MAX) {
+			perror("buffer overflow");
+			continue;
+		}
+		/*
+                 * From man proc: For  file  descriptors  that  have no
+                 * corresponding inode (e.g., file descriptors produced by
+                 * bpf(2)..), the  entry  will be a symbolic link with contents
+                 * of the form:
+                 *      anon_inode:<file-type>
+                 */
+		if (strstr(buf, "anon_inode:seccomp notify") != NULL)
+			return atoi(dp->d_name);
+	}
+	fprintf(stderr, "seccomp notifier not found in %s\n", path);
+	return -1;
+}