tail: fix the checks if the file was rotated

The freopen(3) was replaced with fileargs_open(3) and fclose(3).
In the following function, we skip if the stream is standard in, so it is
safe to do so.
This also requires us to change the logic first to open the file and then
check its status. The stat(2) is disallowed in capability mode.

This commit unbrakes the -F option.
The bug was introduced in the r348708.

Reported by:	pho
Tested by:	pho

usr.bin/tail/extern.h

@@ -78,3 +78,4 @@ int maparound(struct mapinfo *, off_t);
 void printfn(const char *, int);
 
 extern int Fflag, fflag, qflag, rflag, rval, no_files;
+extern fileargs_t *fa;

usr.bin/tail/forward.c

@@ -57,6 +57,9 @@ static const char sccsid[] = "@(#)forward.c	8.1 (Berkeley) 6/6/93";
 #include <string.h>
 #include <unistd.h>
 
+#include <libcasper.h>
+#include <casper/cap_fileargs.h>
+
 #include "extern.h"
 
 static void rlines(FILE *, const char *fn, off_t, struct stat *);
@@ -310,6 +313,7 @@ follow(file_info_t *files, enum STYLE style, off_t off)
 	int active, ev_change, i, n = -1;
 	struct stat sb2;
 	file_info_t *file;
+	FILE *ftmp;
 	struct timespec ts;
 
 	/* Position each of the files */
@@ -346,7 +350,9 @@ follow(file_info_t *files, enum STYLE style, off_t off)
 		if (Fflag) {
 			for (i = 0, file = files; i < no_files; i++, file++) {
 				if (!file->fp) {
-					file->fp = fopen(file->file_name, "r");
+					file->fp =
+					    fileargs_fopen(fa, file->file_name,
+					    "r");
 					if (file->fp != NULL &&
 					    fstat(fileno(file->fp), &file->st)
 					    == -1) {
@@ -359,7 +365,9 @@ follow(file_info_t *files, enum STYLE style, off_t off)
 				}
 				if (fileno(file->fp) == STDIN_FILENO)
 					continue;
-				if (stat(file->file_name, &sb2) == -1) {
+				ftmp = fileargs_fopen(fa, file->file_name, "r");
+				if (ftmp == NULL ||
+				    fstat(fileno(file->fp), &sb2) == -1) {
 					if (errno != ENOENT)
 						ierr(file->file_name);
 					show(file);
@@ -367,6 +375,9 @@ follow(file_info_t *files, enum STYLE style, off_t off)
 						fclose(file->fp);
 						file->fp = NULL;
 					}
+					if (ftmp != NULL) {
+						fclose(ftmp);
+					}
 					ev_change++;
 					continue;
 				}
@@ -375,14 +386,13 @@ follow(file_info_t *files, enum STYLE style, off_t off)
 				    sb2.st_dev != file->st.st_dev ||
 				    sb2.st_nlink == 0) {
 					show(file);
-					file->fp = freopen(file->file_name, "r",
+					fclose(file->fp);
-					    file->fp);
+					file->fp = ftmp;
-					if (file->fp != NULL)
+					memcpy(&file->st, &sb2,
-						memcpy(&file->st, &sb2,
+					    sizeof(struct stat));
-						    sizeof(struct stat));
-					else if (errno != ENOENT)
-						ierr(file->file_name);
 					ev_change++;
+				} else {
+					fclose(ftmp);
 				}
 			}
 		}

usr.bin/tail/misc.c

@@ -51,6 +51,9 @@ static const char sccsid[] = "@(#)misc.c	8.1 (Berkeley) 6/6/93";
 #include <string.h>
 #include <unistd.h>
 
+#include <libcasper.h>
+#include <casper/cap_fileargs.h>
+
 #include "extern.h"
 
 void

usr.bin/tail/read.c

@@ -51,6 +51,9 @@ static const char sccsid[] = "@(#)read.c	8.1 (Berkeley) 6/6/93";
 #include <string.h>
 #include <unistd.h>
 
+#include <libcasper.h>
+#include <casper/cap_fileargs.h>
+
 #include "extern.h"
 
 /*

usr.bin/tail/reverse.c

@@ -55,6 +55,9 @@ __FBSDID("$FreeBSD$");
 #include <string.h>
 #include <unistd.h>
 
+#include <libcasper.h>
+#include <casper/cap_fileargs.h>
+
 #include "extern.h"
 
 static void r_buf(FILE *, const char *);

usr.bin/tail/tail.c

@@ -65,6 +65,7 @@ static const char sccsid[] = "@(#)tail.c	8.1 (Berkeley) 6/6/93";
 #include "extern.h"
 
 int Fflag, fflag, qflag, rflag, rval, no_files;
+fileargs_t *fa;
 
 static file_info_t *files;
 
@@ -90,10 +91,9 @@ main(int argc, char *argv[])
 	int i, ch, first;
 	file_info_t *file;
 	char *p;
-	fileargs_t *fa;
 	cap_rights_t rights;
 
-	cap_rights_init(&rights, CAP_FSTAT, CAP_FCNTL, CAP_MMAP_RW);
+	cap_rights_init(&rights, CAP_FSTAT, CAP_FSTATFS, CAP_FCNTL, CAP_MMAP_RW);
 	if (caph_rights_limit(STDIN_FILENO, &rights) < 0 ||
 	    caph_limit_stderr() < 0 || caph_limit_stdout() < 0)
 		err(1, "can't limit stdio rights");