check_swap: Fix perfdata und thresholds for big values and simplify code

The original problem was https://github.com/monitoring-plugins/monitoring-plugins/pull/1705
where the performance data output of check_swap did not conform to
the parser logic of a monitoring system (which decided to go for
"correct" SI or IEC units.
The PR was accompanied by a change to byte values in the performance
data which broke the _perfdata_ helper function which could not handle
values of this size.
The fix for this, was to use _fperfdata_ which could, but would
use float values.

I didn't like that (since all values here are discreet) and this
is my proposal for a fix for the problem.

It introduces some helper functions which do now explicitely work
with (u)int64_t, including a special version of the _perfdata_ helper.

In the process of introducing this to check_swap, I stumbled over
several sections of the check_swap code which I found problematic.
Therefore I tried to simplify the code and make it more readable
and less redundant.

I am kinda sorry about this, but sincerely hope my changes can
be helpful.

1 files changed, 137 insertions, 102 deletions

diff --git a/plugins/check_swap.c b/plugins/check_swap.c
index 0ff0c770..25bcb3d5 100644
--- a/plugins/check_swap.c
+++ b/plugins/check_swap.c
@@ -34,6 +34,10 @@ const char *email = "devel@monitoring-plugins.org";
 #include "common.h"
 #include "popen.h"
 #include "utils.h"
+#include <string.h>
+#include <math.h>
+#include <libintl.h>
+#include <stdbool.h>
 
 #ifdef HAVE_DECL_SWAPCTL
 # ifdef HAVE_SYS_PARAM_H
@@ -51,26 +55,30 @@ const char *email = "devel@monitoring-plugins.org";
 # define SWAP_CONVERSION 1
 #endif
 
-int check_swap (int usp, float free_swap_mb, float total_swap_mb);
+typedef struct {
+        bool is_percentage;
+        uint64_t value;
+} threshold_t;
+
+int check_swap (float free_swap_mb, float total_swap_mb);
 int process_arguments (int argc, char **argv);
 int validate_arguments (void);
 void print_usage (void);
 void print_help (void);
 
-int warn_percent = 0;
-int crit_percent = 0;
-float warn_size_bytes = 0;
-float crit_size_bytes = 0;
+threshold_t warn;
+threshold_t crit;
 int verbose;
-int allswaps;
+bool allswaps;
 int no_swap_state = STATE_CRITICAL;
 
 int
 main (int argc, char **argv)
 {
-        int percent_used, percent;
-        float total_swap_mb = 0, used_swap_mb = 0, free_swap_mb = 0;
-        float dsktotal_mb = 0, dskused_mb = 0, dskfree_mb = 0, tmp_mb = 0;
+        unsigned int percent_used, percent;
+        uint64_t total_swap_mb = 0, used_swap_mb = 0, free_swap_mb = 0;
+        uint64_t dsktotal_mb = 0, dskused_mb = 0, dskfree_mb = 0;
+        uint64_t tmp_KB = 0;
         int result = STATE_UNKNOWN;
         char input_buffer[MAX_INPUT_BUFFER];
 #ifdef HAVE_PROC_MEMINFO
@@ -116,10 +124,15 @@ main (int argc, char **argv)
         }
         fp = fopen (PROC_MEMINFO, "r");
         while (fgets (input_buffer, MAX_INPUT_BUFFER - 1, fp)) {
-                if (sscanf (input_buffer, "%*[S]%*[w]%*[a]%*[p]%*[:] %f %f %f", &dsktotal_mb, &dskused_mb, &dskfree_mb) == 3) {
-                        dsktotal_mb = dsktotal_mb / 1048576;    /* Apply conversion */
-                        dskused_mb = dskused_mb / 1048576;
-                        dskfree_mb = dskfree_mb / 1048576;
+                /*
+                 * The following sscanf call looks for a line looking like: "Swap: 123 123 123"
+                 * On which kind of system this format exists, I can not say, but I wanted to
+                 * document this for people who are not adapt with sscanf anymore, like me
+                 */
+                if (sscanf (input_buffer, "%*[S]%*[w]%*[a]%*[p]%*[:] %lu %lu %lu", &dsktotal_mb, &dskused_mb, &dskfree_mb) == 3) {
+                        dsktotal_mb = dsktotal_mb / (1024 * 1024);      /* Apply conversion */
+                        dskused_mb = dskused_mb / (1024 * 1024);
+                        dskfree_mb = dskfree_mb / (1024 * 1024);
                         total_swap_mb += dsktotal_mb;
                         used_swap_mb += dskused_mb;
                         free_swap_mb += dskfree_mb;
@@ -128,21 +141,25 @@ main (int argc, char **argv)
                                         percent=100.0;
                                 else
                                         percent = 100 * (((double) dskused_mb) / ((double) dsktotal_mb));
-                                result = max_state (result, check_swap (percent, dskfree_mb, dsktotal_mb));
+                                result = max_state (result, check_swap (dskfree_mb, dsktotal_mb));
                                 if (verbose)
                                         xasprintf (&status, "%s [%.0f (%d%%)]", status, dskfree_mb, 100 - percent);
                         }
                 }
-                else if (sscanf (input_buffer, "%*[S]%*[w]%*[a]%*[p]%[TotalFre]%*[:] %f %*[k]%*[B]", str, &tmp_mb)) {
+                /*
+                 * The following sscanf call looks for lines looking like: "SwapTotal: 123" and "SwapFree: 123"
+                 * This format exists at least on Debian Linux with a 5.* kernel
+                 */
+                else if (sscanf (input_buffer, "%*[S]%*[w]%*[a]%*[p]%[TotalFre]%*[:] %lu %*[k]%*[B]", str, &tmp_KB)) {
                         if (verbose >= 3) {
-                                printf("Got %s with %f\n", str, tmp_mb);
+                                printf("Got %s with %lu\n", str, tmp_KB);
                         }
                         /* I think this part is always in Kb, so convert to mb */
                         if (strcmp ("Total", str) == 0) {
-                                dsktotal_mb = tmp_mb / 1024;
+                                dsktotal_mb = tmp_KB / 1024;
                         }
                         else if (strcmp ("Free", str) == 0) {
-                                dskfree_mb = tmp_mb / 1024;
+                                dskfree_mb = tmp_KB / 1024;
                         }
                 }
         }
@@ -227,7 +244,7 @@ main (int argc, char **argv)
                         free_swap_mb += dskfree_mb;
                         if (allswaps) {
                                 percent = 100 * (((double) dskused_mb) / ((double) dsktotal_mb));
-                                result = max_state (result, check_swap (percent, dskfree_mb, dsktotal_mb));
+                                result = max_state (result, check_swap (dskfree_mb, dsktotal_mb));
                                 if (verbose)
                                         xasprintf (&status, "%s [%.0f (%d%%)]", status, dskfree_mb, 100 - percent);
                         }
@@ -289,7 +306,7 @@ main (int argc, char **argv)
 
                 if(allswaps && dsktotal_mb > 0){
                         percent = 100 * (((double) dskused_mb) / ((double) dsktotal_mb));
-                        result = max_state (result, check_swap (percent, dskfree_mb, dsktotal_mb));
+                        result = max_state (result, check_swap (dskfree_mb, dsktotal_mb));
                         if (verbose) {
                                 xasprintf (&status, "%s [%.0f (%d%%)]", status, dskfree_mb, 100 - percent);
                         }
@@ -328,7 +345,7 @@ main (int argc, char **argv)
 
                 if(allswaps && dsktotal_mb > 0){
                         percent = 100 * (((double) dskused_mb) / ((double) dsktotal_mb));
-                        result = max_state (result, check_swap (percent, dskfree_mb, dsktotal_mb));
+                        result = max_state (result, check_swap(dskfree_mb, dsktotal_mb));
                         if (verbose) {
                                 xasprintf (&status, "%s [%.0f (%d%%)]", status, dskfree_mb, 100 - percent);
                         }
@@ -355,14 +372,19 @@ main (int argc, char **argv)
                 status = "- Swap is either disabled, not present, or of zero size. ";
         }
 
-        result = max_state (result, check_swap (percent_used, free_swap_mb, total_swap_mb));
-        printf (_("SWAP %s - %d%% free (%d MB out of %d MB) %s|"),
+        result = max_state (result, check_swap(free_swap_mb, total_swap_mb));
+        printf (_("SWAP %s - %d%% free (%dMB out of %dMB) %s|"),
                         state_text (result),
                         (100 - percent_used), (int) free_swap_mb, (int) total_swap_mb, status);
 
-        puts (perfdata ("swap", (long) free_swap_mb, "MB",
-                        TRUE, (long) max (warn_size_bytes/(1024 * 1024), warn_percent/100.0*total_swap_mb),
-                        TRUE, (long) max (crit_size_bytes/(1024 * 1024), crit_percent/100.0*total_swap_mb),
+        uint64_t warn_print = warn.value;
+        if (warn.is_percentage) warn_print = warn.value * (total_swap_mb *1024 *1024/100);
+        uint64_t crit_print = crit.value;
+        if (crit.is_percentage) crit_print = crit.value * (total_swap_mb *1024 *1024/100);
+
+        puts (perfdata_uint64 ("swap", free_swap_mb *1024 *1024, "B",
+                        TRUE, warn_print,
+                        TRUE, crit_print,
                         TRUE, 0,
                         TRUE, (long) total_swap_mb));
 
@@ -370,26 +392,37 @@ main (int argc, char **argv)
 }
 
 
-
 int
-check_swap (int usp, float free_swap_mb, float total_swap_mb)
+check_swap(float free_swap_mb, float total_swap_mb)
 {
 
         if (!total_swap_mb) return no_swap_state;
 
-        int result = STATE_UNKNOWN;
-        float free_swap = free_swap_mb * (1024 * 1024);         /* Convert back to bytes as warn and crit specified in bytes */
-        if (usp >= 0 && crit_percent != 0 && usp >= (100.0 - crit_percent))
-                result = STATE_CRITICAL;
-        else if (crit_size_bytes > 0 && free_swap <= crit_size_bytes)
-                result = STATE_CRITICAL;
-        else if (usp >= 0 && warn_percent != 0 && usp >= (100.0 - warn_percent))
-                result = STATE_WARNING;
-        else if (warn_size_bytes > 0 && free_swap <= warn_size_bytes)
-                result = STATE_WARNING;
-        else if (usp >= 0.0)
-                result = STATE_OK;
-        return result;
+        uint64_t free_swap = free_swap_mb * (1024 * 1024);              /* Convert back to bytes as warn and crit specified in bytes */
+
+        if (!crit.is_percentage && crit.value <= free_swap) return STATE_CRITICAL;
+        if (!warn.is_percentage && warn.value <= free_swap) return STATE_WARNING;
+
+
+        uint64_t usage_percentage = ((total_swap_mb - free_swap_mb) / total_swap_mb) * 100;
+
+        if (crit.is_percentage &&
+                        usage_percentage >= 0 &&
+                        crit.value != 0 &&
+                        usage_percentage >= (100 - crit.value))
+        {
+                        return STATE_CRITICAL;
+        }
+
+        if (warn.is_percentage &&
+                        usage_percentage >= 0 &&
+                        warn.value != 0 &&
+                        usage_percentage >= (100 - warn.value))
+        {
+                        return STATE_WARNING;
+        }
+
+        return STATE_OK;
 }
 
 
@@ -422,42 +455,67 @@ process_arguments (int argc, char **argv)
                         break;
 
                 switch (c) {
-                case 'w':                                                                       /* warning size threshold */
-                        if (is_intnonneg (optarg)) {
-                                warn_size_bytes = (float) atoi (optarg);
-                                break;
-                        }
-                        else if (strstr (optarg, ",") &&
-                                                         strstr (optarg, "%") &&
-                                                         sscanf (optarg, "%f,%d%%", &warn_size_bytes, &warn_percent) == 2) {
-                                warn_size_bytes = floorf(warn_size_bytes);
-                                break;
-                        }
-                        else if (strstr (optarg, "%") &&
-                                                         sscanf (optarg, "%d%%", &warn_percent) == 1) {
-                                break;
-                        }
-                        else {
-                                usage4 (_("Warning threshold must be integer or percentage!"));
-                        }
-                case 'c':                                                                       /* critical size threshold */
-                        if (is_intnonneg (optarg)) {
-                                crit_size_bytes = (float) atoi (optarg);
-                                break;
-                        }
-                        else if (strstr (optarg, ",") &&
-                                                         strstr (optarg, "%") &&
-                                                         sscanf (optarg, "%f,%d%%", &crit_size_bytes, &crit_percent) == 2) {
-                                crit_size_bytes = floorf(crit_size_bytes);
-                                break;
-                        }
-                        else if (strstr (optarg, "%") &&
-                                                         sscanf (optarg, "%d%%", &crit_percent) == 1) {
-                                break;
-                        }
-                        else {
-                                usage4 (_("Critical threshold must be integer or percentage!"));
+                case 'w': /* warning size threshold */
+                        {
+                                /*
+                                 * We expect either a positive integer value without a unit, which means
+                                 * the unit is Bytes or a positive integer value and a percentage sign (%),
+                                 * which means the value must be with 0 and 100 and is relative to the total swap
+                                 */
+                                size_t length;
+                                length = strlen(optarg);
+
+                                if (optarg[length - 1] == '%') {
+                                        // It's percentage!
+                                        warn.is_percentage = true;
+                                        optarg[length - 1] = '\0';
+                                        if (is_uint64(optarg, &warn.value)) {
+                                                if (warn.value > 100) {
+                                                        usage4 (_("Warning threshold percentage must be <= 100!"));
+                                                } else {
+                                                        break;
+                                                }
+                                        }
+                                } else {
+                                        // It's Bytes
+                                        warn.is_percentage = false;
+                                        if (is_uint64(optarg, &warn.value)) {
+                                                break;
+                                        } else {
+                                                usage4 (_("Warning threshold be positive integer or percentage!"));
+                                        }
+                                }
                         }
+                case 'c': /* critical size threshold */
+                        {
+                                /*
+                                 * We expect either a positive integer value without a unit, which means
+                                 * the unit is Bytes or a positive integer value and a percentage sign (%),
+                                 * which means the value must be with 0 and 100 and is relative to the total swap
+                                 */
+                                size_t length;
+                                length = strlen(optarg);
+
+                                if (optarg[length - 1] == '%') {
+                                        // It's percentage!
+                                        crit.is_percentage = true;
+                                        optarg[length - 1] = '\0';
+                                        if (is_uint64(optarg, &crit.value)) {
+                                                if (crit.value> 100) {
+                                                        usage4 (_("Critical threshold percentage must be <= 100!"));
+                                                } else {
+                                                        break;
+                                                }
+                                        }
+                                } else {
+                                        crit.is_percentage = false;
+                                        if (is_uint64(optarg, &crit.value)) {
+                                                break;
+                                        } else {
+                                                usage4 (_("Critical threshold be positive integer or percentage!"));
+                                        }
+                                }
+                          }
                 case 'a':                                                                       /* all swap */
                         allswaps = TRUE;
                         break;
@@ -482,23 +540,6 @@ process_arguments (int argc, char **argv)
         c = optind;
         if (c == argc)
                 return validate_arguments ();
-        if (warn_percent == 0 && is_intnonneg (argv[c]))
-                warn_percent = atoi (argv[c++]);
-
-        if (c == argc)
-                return validate_arguments ();
-        if (crit_percent == 0 && is_intnonneg (argv[c]))
-                crit_percent = atoi (argv[c++]);
-
-        if (c == argc)
-                return validate_arguments ();
-        if (warn_size_bytes == 0 && is_intnonneg (argv[c]))
-                warn_size_bytes = (float) atoi (argv[c++]);
-
-        if (c == argc)
-                return validate_arguments ();
-        if (crit_size_bytes == 0 && is_intnonneg (argv[c]))
-                crit_size_bytes = (float) atoi (argv[c++]);
 
         return validate_arguments ();
 }
@@ -508,17 +549,12 @@ process_arguments (int argc, char **argv)
 int
 validate_arguments (void)
 {
-        if (warn_percent == 0 && crit_percent == 0 && warn_size_bytes == 0
-                        && crit_size_bytes == 0) {
+        if (warn.value == 0 && crit.value == 0) {
                 return ERROR;
         }
-        else if (warn_percent < crit_percent) {
-                usage4
-                        (_("Warning percentage should be more than critical percentage"));
-        }
-        else if (warn_size_bytes < crit_size_bytes) {
+        else if (warn.value < crit.value) {
                 usage4
-                        (_("Warning free space should be more than critical free space"));
+                        (_("Warning should be more than critical"));
         }
         return OK;
 }
@@ -564,7 +600,6 @@ print_help (void)
 }
 
 
-
 void
 print_usage (void)
 {