From 41ca93fc94cfef39a146f94e4ba3e6fa25497d53 Mon Sep 17 00:00:00 2001
From: Glenn <glenux@glenux.net>
Date: Tue, 26 Dec 2023 11:13:13 +0100
Subject: [PATCH] feat: implement basic packet creation

---
 src/igmpgen.c | 76 +++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 64 insertions(+), 12 deletions(-)

diff --git a/src/igmpgen.c b/src/igmpgen.c
index 855d108..6081e39 100644
--- a/src/igmpgen.c
+++ b/src/igmpgen.c
@@ -21,6 +21,7 @@ struct igmp_extra {
     { 2, "query",  0x11, 1, "224.0.0.1", 0 },
     { 2, "report", 0x16, 1, "224.0.0.2", 1 },
     { 2, "leave",  0x17, 1, "224.0.0.2", 0 },
+
     /* Note: end of list (please keep) */
     { 0, 0, 0, 0 },
 };
@@ -32,17 +33,22 @@ void usage(char *name)
 
 int main(int argc, char **argv)
 {
-    /* ip addresses */
     u_int32_t ip_src = 0;
     char *ip_src_str = NULL;
-
     /* libnet stuff */
     char neterr[LIBNET_ERRBUF_SIZE];
     libnet_t *netcontext = NULL;
 
     /* misc */
-    int c;                      
+    int c;
     char *device = NULL;
+    u_int8_t igmp_version = 0;
+    char *cp = NULL;
+    int found = 0;
+    struct igmp_extra *pkt_ptr;
+    u_char igmp_type = 0;
+    u_char igmp_code = 0;
+
     printf("IGMP packet generator\n\n");
 
     printf("Parsing command line...\n");
@@ -55,8 +61,27 @@ int main(int argc, char **argv)
                 device = optarg;
                 break;
             case 't':
-                /* Packet version/type argument handling */
-                printf("  Packet version/type = [%s]\n", optarg);
+                if (!(cp = strrchr(optarg, '.'))) {
+                    usage(argv[0]);
+                    exit(1);
+                }
+                *cp++ = 0;
+                igmp_version = (u_short)atoi(cp);
+                pkt_ptr = g_igmp_pkts;
+                while (pkt_ptr->igmp_version || pkt_ptr->igmp_tag) {
+                    if ((strcasecmp(pkt_ptr->igmp_tag, optarg) == 0) 
+                        && (igmp_version == pkt_ptr->igmp_version)) {
+                        found = 1;
+                        igmp_type = pkt_ptr->igmp_type;
+                        igmp_code = pkt_ptr->igmp_code;
+                        break;
+                    }
+                    pkt_ptr++;
+                }
+                if (!found) {
+                    usage(argv[0]);
+                    exit(1);
+                }
                 break;
             default:
                 usage(argv[0]);
@@ -72,22 +97,49 @@ int main(int argc, char **argv)
     printf("done\n");
 
     /* Memory initialization */
-    printf("Initializing libnet context...");
+    printf("Initializing libnet context...\n");
     netcontext = libnet_init(LIBNET_RAW4, device, neterr);
-    if (!netcontext){
-        fprintf(stderr, neterr);
+    if (!netcontext) {
+        fprintf(stderr, "%s\n", neterr);
         exit(1);
     }
     libnet_clear_packet(netcontext);
-    if (!ip_src_str)
-    {
+
+    if (!ip_src_str) {
         ip_src = libnet_get_ipaddr4(netcontext);
         ip_src_str = libnet_addr2name4(ip_src, LIBNET_DONT_RESOLVE);
     }
 
-    printf("done\n");
+    printf("Packet construction...\n");
+
+    /* Packet construction: IGMP */
+    printf("  Building IGMP content...\n");
+    libnet_ptag_t ptag;
+    ptag = libnet_build_igmp(
+        igmp_type,        // IGMP type
+        igmp_code,        // IGMP code
+        0,                // checksum
+        0,                // group address
+        NULL,             // payload
+        0,                // payload size
+        netcontext,       // libnet context
+        0                 // ptag
+    );
+    if (ptag == -1) {
+        fprintf(stderr, "Error building IGMP header: %s\n", libnet_geterror(netcontext));
+        libnet_destroy(netcontext);
+        exit(EXIT_FAILURE);
+    }
+
+    printf("  done\n");
+
+    /* Send packet */
+    if (libnet_write(netcontext) == -1) {
+        fprintf(stderr, "Error sending packet: %s\n", libnet_geterror(netcontext));
+    } else {
+        printf("Packet sent successfully.\n");
+    }
 
-    /* Clean up and exit */
     libnet_destroy(netcontext);
     return 0;
 }