Add IP address ranges and make allowing broadcasts on sending socket optionalHEADmaster

1 files changed, 120 insertions, 13 deletions

diff --git a/udprelay.c b/udprelay.c
index 94781b6..033ec19 100644
--- a/udprelay.c
+++ b/udprelay.c
@@ -26,6 +26,18 @@
 #include <arpa/inet.h>
 #include <stdio.h>
 #include <linux/if.h>
+#include <stdlib.h>
+
+int numcharsinstr(char *str, char ch) {
+  int i, count = 0;
+
+  for (i = 0; str[i] != '\0'; i++) {
+    if (str[i] == ch)
+      count++;
+  }
+
+  return count;
+}
 
 int main(int argc, char *argv[]) {
 
@@ -37,10 +49,100 @@ int main(int argc, char *argv[]) {
     int rcvfd;
     int sndfd;
 
+    /* For for loops */
+    int i, j;
+
+    /* Destination addresses passed in */
+    unsigned long addrcount = 0;
+    int addressessize = 1024;
+    int* addresses = malloc(addressessize * sizeof(int));
+
+    /* argc offset to take into account -b or not */
+    int argo = 4;
+
+    /* Do we want to enable sending to a broadcast address? */
+    short broadcast = 0;
+
+    if (argc > 1 && !strcmp(argv[1], "-b")) {
+      broadcast = 1;
+      argo++;
+    }
+
+    /* See if we're dealing with a destination address range */
+    for (i = 0; i < argc - argo; i++) {
+      /* Make sure there are zero or one range separators */
+      if (numcharsinstr(argv[i + argo], '-') > 1) {
+        fprintf(stderr, "Too many range separators (-): %s\n", argv[i + argo]);
+        return 1;
+      /* We're using a range */
+      } else if (numcharsinstr(argv[i + argo], '-') == 1) {
+        int ip1, ip2, rangelen;
+
+        char *tok = NULL;
+        char *ptr;
+
+        tok = strtok(argv[i + argo], "-");
+        if ((inet_pton(AF_INET, tok, &ip1)) != 1) {
+          fprintf(stderr, "First IP in range is invalid\n");
+          return 1;
+        }
+        ip1 = htonl(ip1);
+
+        tok = strtok(NULL, "-");
+        if ((inet_pton(AF_INET, tok, &ip2)) != 1) {
+          fprintf(stderr, "Second IP in range is invalid\n");
+          return 1;
+        }
+        ip2 = htonl(ip2);
+
+        /* Length of range */
+        rangelen = ip2 - ip1 + 1;
+
+        if (rangelen < 1) {
+          fprintf(stderr, "Range is less than one address long "
+                          "(higher address before lower address?)\n");
+          return 1;
+        }
+
+        // Debugging:
+        // printf("IP range is %d addresses long\n", rangelen);
+        if (addrcount + rangelen > addressessize) {
+          while (addrcount + rangelen > addressessize) {
+            addressessize *= 2;
+          }
+          addresses = realloc(addresses, addressessize * sizeof(int));
+        }
+
+        for (j = 0; j < rangelen; j++) {
+          addresses[addrcount + j] = ip1 + j;
+        }
+        addrcount += rangelen;
+
+        /* Limit to around 2^18 addresses because doubling
+           again leads to struct size problems
+        */
+        if (addrcount > 262144) {
+          fprintf(stderr, "Range of addresses is too great\n");
+          return 1;
+        }
+      /* It's a single address */
+      } else {
+        int ip;
+
+        if ((inet_pton(AF_INET, argv[i + argo], &ip)) != 1) {
+          fprintf(stderr, "IP address is invalid\n");
+            return 1;
+        }
+
+        addresses[addrcount] = htonl(ip);
+        addrcount++;
+      }
+    }
+
     /* Destination addresses */
     struct {
         struct sockaddr_in dstaddr;
-    } dsts[argc - 4]; /* Anything after 4th arg is a destination address */
+    } dsts[addrcount];
     /* Number of destination addresses */
     int dstcount;
 
@@ -53,8 +155,6 @@ int main(int argc, char *argv[]) {
     /* Address of source packet */
     struct sockaddr_in srcaddr;
 
-    /* For for loops */
-    int i;
     /* For setsockopt() values */
     int optval;
 
@@ -72,12 +172,20 @@ int main(int argc, char *argv[]) {
 
     /* Print some usage instructions */
     if (argc < 5) {
-        fprintf(stderr, "Usage: %s LST-ADDR LST-PORT DST-PORT DST-ADDR [DST-ADDR]...\n"
+        fprintf(stderr, "Usage: %s [-b] LST-ADDR LST-PORT DST-PORT DST-ADDR [DST-ADDR]...\n"
+                        "\n"
+                        "-b  Allow sending to a broadcast address.  Beware, this can\n"
+                        "    create a broadcast storm if retransmitting to a broadcast\n"
+                        "    address on the same port a packet came in on.\n"
                         "\n"
                         "bind()s to address LST-ADDR on port LST-PORT and retransmits UDP\n"
                         "packets received to addresses(s) DST-ADDR(s) on port DST-PORT,\n"
                         "with modified headers to reflect the new target.\n"
                         "\n"
+                        "DST-ADDR can be a range of IP addresses in the form:\n"
+                        "a.b.c.d-w.x.y.z e.g. 10.0.0.1-10.0.1.254\n"
+                        "Note that this may include a broadcast address (see above).\n"
+                        "\n"
                         "To receieve broadcast traffic, use a LST-ADDR of 0.0.0.0.  If\n"
                         "a program is already listening on LST-PORT on LST-ADDR, you may\n"
                         "listen on a broadcast address such as 255.255.255.255.\n"
@@ -91,7 +199,7 @@ int main(int argc, char *argv[]) {
         return 1;
     }
 
-    if (((lstport = atoi(argv[2])) == 0) || ((dstport = atoi(argv[3])) == 0)) {
+    if (((lstport = atoi(argv[argo - 2])) == 0) || ((dstport = atoi(argv[argo - 1])) == 0)) {
         fprintf(stderr, "lst-port or dst-port is invalid\n");
         return 1;
     }
@@ -109,14 +217,13 @@ int main(int argc, char *argv[]) {
     rcvmsg.msg_controllen = sizeof(pkt_info);
 
     /* Enumerate destination addresses */
-    for (i = 0; i < argc - 4; i++) {
+    for (i = 0; i < addrcount; i++) {
         dsts[i].dstaddr.sin_family = AF_INET;
         dsts[i].dstaddr.sin_port = htons(dstport);
-        if ((inet_pton(AF_INET, argv[i + 4], &dsts[i].dstaddr.sin_addr)) != 1) {
-            fprintf(stderr, "dst-addr%d is invalid\n", i + 1);
-            return 1;
-        }
+        /* Populate sin_addr straight from our numeric addresses */
+        dsts[i].dstaddr.sin_addr.s_addr = ntohl(addresses[i]);
     }
+
     /* Set number of destinations */
     dstcount = i;
 
@@ -136,7 +243,7 @@ int main(int argc, char *argv[]) {
     /* Set properties of source address */
     srcaddr.sin_family = AF_INET;
     srcaddr.sin_port = htons(lstport);
-    if ((inet_pton(AF_INET, argv[1], &srcaddr.sin_addr.s_addr)) != 1) {
+    if ((inet_pton(AF_INET, argv[argo - 3], &srcaddr.sin_addr.s_addr)) != 1) {
         fprintf(stderr, "lst-addr is invalid\n");
         return 1;
     }
@@ -153,8 +260,8 @@ int main(int argc, char *argv[]) {
         return 1;
     }
 
-    /* Allow UDP broadcasts on sending socket */
-    if (setsockopt(sndfd, SOL_SOCKET, SO_BROADCAST, &optval, sizeof(int)) < 0) {
+    /* Allow UDP broadcasts on sending socket if requested */
+    if (broadcast && setsockopt(sndfd, SOL_SOCKET, SO_BROADCAST, &optval, sizeof(int)) < 0) {
         perror("setsockopt(sndfd, SOL_SOCKET, SO_BROADCAST, ...)");
         return 1;
     }