feat: add -M (dont-fragment) option

- Add FLAG_DONT_FRAGMENT flag and cli_handle_dont_fragment handler
- Register -M/--dont-fragment option in the X-macro option table
- Apply DF bit via icmp_set_dont_fragment() before ping loop
- Expand error output: table-driven ICMP error messages and dedicated
  frag-needed output with next-hop MTU
- Add STATIC_ARRAY_FOREACH / COUNT_OF macros to compiler.h

includes/compiler.h

@@ -3,4 +3,9 @@
 
 #define __unused __attribute__((unused))
 
+#define COUNT_OF(arr) (sizeof(arr) / sizeof((arr)[0]))
+
+#define STATIC_ARRAY_FOREACH(arr, ptr) \
+	for ((ptr) = (arr); (ptr) < (arr) + COUNT_OF(arr); (ptr)++)
+
 #endif

includes/internal/cli/options.h

@@ -91,6 +91,14 @@
 		cli_handle_flood, \
 		OPT_ARG_NONE, \
 		"Flood mode" \
+	) \
+	X( \
+		'M', \
+		"dont-fragment", \
+		no_argument, \
+		cli_handle_dont_fragment, \
+		OPT_ARG_NONE, \
+		"Set the Don't Fragment bit" \
 	)
 
 #undef X

includes/internal/ping/cli_handlers.h

@@ -6,6 +6,7 @@
 extern const struct option_descriptor	g_options[];
 
 int	cli_handle_count(const char *arg, void *config);
+int	cli_handle_dont_fragment(const char *arg, void *config);
 int	cli_handle_deadline(const char *arg, void *config);
 int	cli_handle_flood(const char *arg, void *config);
 int	cli_handle_help(const char *arg, void *config);

includes/ping/ft_ping_flags.h

@@ -1,9 +1,10 @@
 #ifndef FT_PING_FLAGS
 #define FT_PING_FLAGS
 
-#define FLAG_VERBOSE	(1 << 0)
-#define FLAG_QUIET		(1 << 1)
-#define FLAG_FLOOD		(1 << 2)
+#define FLAG_VERBOSE			(1 << 0)
+#define FLAG_QUIET				(1 << 1)
+#define FLAG_FLOOD				(1 << 2)
+#define FLAG_DONT_FRAGMENT		(1 << 3)
 
 #define HAS_FLAG(flags, flag)		((flags) & (flag))
 #define SET_FLAG(flags, flag)		((flags) |= (flag))

sources/ping.mk

@@ -6,6 +6,7 @@ PING_SRCS = $(CLI_SRCS) \
 	   $(PING_SRC_DIR)/main.c \
 	   $(PING_SRC_DIR)/cli/parse.c \
 	   $(PING_SRC_DIR)/cli/handlers/handle_count.c \
+	   $(PING_SRC_DIR)/cli/handlers/handle_dont_fragment.c \
 	   $(PING_SRC_DIR)/cli/handlers/handle_deadline.c \
 	   $(PING_SRC_DIR)/cli/handlers/handle_flood.c \
 	   $(PING_SRC_DIR)/cli/handlers/handle_help.c \

src/cli/parse.c

@@ -96,7 +96,8 @@ static void
 build_long_options(struct option *long_opts, size_t nb_opts,
 		const struct option_descriptor *src)
 {
-	for (size_t i = 0; i < nb_opts; ++i) {
+	for (size_t i = 0; i < nb_opts; ++i)
+	{
 		long_opts[i].name		= src[i].long_opt;
 		long_opts[i].has_arg	= src[i].has_arg;
 		long_opts[i].flag		= NULL;

src/ping/cli/handlers/handle_dont_fragment.c

@@ -0,0 +1,11 @@
+#include "compiler.h"
+#include "ping/cli.h"
+#include "ping/ft_ping_flags.h"
+
+int
+cli_handle_dont_fragment(__unused const char *arg, void *config_void)
+{
+	struct ping_config	*config = (struct ping_config *)config_void;
+	SET_FLAG(config->flags, FLAG_DONT_FRAGMENT);
+	return CLI_SUCCESS;
+}

src/ping/core/ping.c

@@ -25,22 +25,28 @@ int
 ping_run(const struct ping_config *config)
 {
 	icmp_handle_t	*handle;
-	int				ret;
-	size_t			i;
+	int				ret = 0 ;
+	size_t			i = 0 ;
 
 	if (0 == config->nb_destinations)
 		return 1;
 	handle = icmp_create();
 	if (NULL == handle)
 		return 1;
-	ret = 0;
-	i = 0;
+	if (HAS_FLAG(config->flags, FLAG_DONT_FRAGMENT)
+			&& 0 != icmp_set_dont_fragment(handle))
+	{
+		ret = 1;
+		goto cleanup;
+	}
+
 	while (i < config->nb_destinations)
 	{
 		if (0 != ping_one(config, config->destinations[i], handle))
 			ret = 1;
 		i++;
 	}
+cleanup:
 	icmp_destroy(handle);
 	return ret;
 }

src/ping/output/error.c

@@ -1,4 +1,5 @@
 #include <stdio.h>
+#include <unistd.h>
 #include <arpa/inet.h>
 
 #include "compiler.h"
@@ -7,27 +8,82 @@
 #include "icmp_types.h"
 #include "internal/ping/output.h"
 
+// TODO: CLEAN THIS FILE !
 /* Forward declarations */
-static const char *error_msg_for(const icmp_reply_t *reply);
+static void			output_frag_needed(const char *from, uint16_t seq,
+						uint16_t next_mtu);
+static const char	*error_msg_for(const icmp_reply_t *reply);
 /* -------------------- */
 
 void
 ping_output_error(const icmp_reply_t *reply,
-		__unused const icmp_offending_packet_t *offending,
+		const icmp_offending_packet_t *offending,
 		uint16_t seq, __unused const struct ping_config *config)
 {
 	char	from_str[INET_ADDRSTRLEN];
+
 	inet_ntop(AF_INET, &reply->from, from_str, sizeof(from_str));
-	fprintf(stderr, "From %s: icmp_seq=%u %s\n",
-			from_str, (unsigned int)seq, error_msg_for(reply));
+	if (ICMP_TYPE_DEST_UNREACHABLE == reply->type
+			&& ICMP_CODE_FRAG_NEEDED == reply->code)
+		output_frag_needed(from_str, seq, offending->next_mtu);
+	else
+		dprintf(STDERR_FILENO, "From %s: icmp_seq=%u %s\n",
+				from_str, (unsigned int)seq, error_msg_for(reply));
+}
+
+static void
+output_frag_needed(const char *from, uint16_t seq, uint16_t next_mtu)
+{
+	if (next_mtu > 0)
+		dprintf(STDERR_FILENO,
+				"From %s: icmp_seq=%u Frag needed and DF set (mtu = %u)\n",
+				from, (unsigned int)seq, (unsigned int)next_mtu);
+	else
+		dprintf(STDERR_FILENO,
+				"From %s: icmp_seq=%u Frag needed and DF set (mtu unknown)\n",
+				from, (unsigned int)seq);
 }
 
 static const char *
 error_msg_for(const icmp_reply_t *reply)
 {
-	if (ICMP_TYPE_TIME_EXCEEDED == reply->type)
-		return ("Time to live exceeded");
-	if (ICMP_CODE_HOST_UNREACHABLE == reply->code)
-		return ("Destination Host Unreachable");
-	return ("Destination Net Unreachable");
+	static const struct s_error_entry
+	{
+		uint8_t		type;
+		uint8_t		code;
+		const char	*msg;
+	} error_table[] = {
+		{
+			ICMP_TYPE_TIME_EXCEEDED, ICMP_CODE_TTL_EXCEEDED,
+			"Time to live exceeded"
+		},
+		{
+			ICMP_TYPE_TIME_EXCEEDED, ICMP_CODE_FRAG_REASM_EXCEEDED,
+			"Frag reassembly time exceeded"
+		},
+		{
+			ICMP_TYPE_DEST_UNREACHABLE, ICMP_CODE_NET_UNREACHABLE,
+			"Destination Net Unreachable"
+		},
+		{
+			ICMP_TYPE_DEST_UNREACHABLE, ICMP_CODE_HOST_UNREACHABLE,
+			"Destination Host Unreachable"
+		},
+		{
+			ICMP_TYPE_DEST_UNREACHABLE, ICMP_CODE_PROTOCOL_UNREACHABLE,
+			"Destination Protocol Unreachable"
+		},
+		{
+			ICMP_TYPE_DEST_UNREACHABLE, ICMP_CODE_PORT_UNREACHABLE,
+			"Destination Port Unreachable"
+		},
+	};
+	const struct s_error_entry	*entry;
+
+	STATIC_ARRAY_FOREACH(error_table, entry)
+	{
+		if (entry->type == reply->type && entry->code == reply->code)
+			return (entry->msg);
+	}
+	return ("Unknown ICMP error");
 }