xdp-gun: support for target IP in other subnet

diff --git a/src/utils/xdp-gun/main.c b/src/utils/xdp-gun/main.c
index 3ddee0e4819dd9599f024becbeea8ffaee423569..2030eec2b1e7b1c9a297bd3cc214677df2ce4314 100644 (file)
--- a/src/utils/xdp-gun/main.c
+++ b/src/utils/xdp-gun/main.c
@@ -320,6 +320,29 @@ static bool str2mac(const char *str, uint8_t mac[])
        return true;
 }
 
+static int ip_route_get(const char *ip, const char *what, char **res)
+{
+       char cmd[50 + strlen(ip) + strlen(what)];
+       snprintf(cmd, sizeof(cmd), "ip route get %s | grep -o ' %s [^ ]* '", ip, what);
+
+       FILE *p = popen(cmd, "r");
+       if (p == NULL) {
+               return knot_map_errno();
+       }
+
+       char check[16] = { 0 }, got[256] = { 0 };
+       if (fscanf(p, "%15s%255s", check, got) != 2 ||
+           strcmp(check, what) != 0) {
+               int ret = feof(p) ? KNOT_ENOENT : KNOT_EMALF;
+               fclose(p);
+               return ret;
+       }
+       fclose(p);
+
+       *res = strdup(got);
+       return *res == NULL ? KNOT_ENOMEM : KNOT_EOK;
+}
+
 static int remoteIP2MAC(const char *ip_str, bool ipv6, char devname[], uint8_t remote_mac[])
 {
        FILE *p = popen(ipv6 ? "ip -6 neigh" : "arp -ne", "r");
@@ -348,36 +371,39 @@ static int remoteIP2MAC(const char *ip_str, bool ipv6, char devname[], uint8_t r
        return ret;
 }
 
-static int remoteIP2local(const char *ip_str, bool ipv6, char devname[], void *local)
+static int distantIP2MAC(const char *ip_str, bool ipv6, char devname[], uint8_t remote_mac[])
 {
-       char cmd[51 + strlen(ip_str)];
-       strcpy(cmd, "ip route get ");
-       strcat(cmd, ip_str);
-       strcat(cmd, " | sed 's/from :://;s/proto kernel//'");
+       char *via = NULL;
+       int ret = ip_route_get(ip_str, "via", &via);
+       switch (ret) {
+       case KNOT_ENOENT: // same subnet, no via
+               return remoteIP2MAC(ip_str, ipv6, devname, remote_mac);
+       case KNOT_EOK:
+               ret = remoteIP2MAC(via, ipv6, devname, remote_mac);
+               free(via);
+               return ret;
+       default:
+               return ret;
+       }
+}
 
-       FILE *p = popen(cmd, "r");
-       if (p == NULL) {
-               return knot_map_errno();
+static int remoteIP2local(const char *ip_str, bool ipv6, char devname[], void *local)
+{
+       char *dev = NULL, *loc = NULL;
+       int ret = ip_route_get(ip_str, "dev", &dev);
+       if (ret != KNOT_EOK) {
+               return ret;
        }
+       strncpy(devname, dev, IFNAMSIZ);
+       free(dev);
 
-       char line_buf[1024] = { 0 };
-       int ret = KNOT_ENOENT;
-       while (fgets(line_buf, sizeof(line_buf) - 1, p) != NULL && ret == KNOT_ENOENT) {
-               char fields[7][strlen(line_buf)];
-               if (sscanf(line_buf, "%s%s%s%s%s%s%s", fields[0], fields[1], fields[2], fields[3], fields[4], fields[5], fields[6]) != 7) {
-                       continue;
-               }
-               if (strcmp(fields[0], ip_str) != 0) {
-                       continue;
-               }
-               if (inet_pton(ipv6 ? AF_INET6 : AF_INET, fields[4], local) <= 0) {
-                       ret = KNOT_EMALF;
-               } else {
-                       strlcpy(devname, fields[2], IFNAMSIZ);
-                       ret = KNOT_EOK;
-               }
+       ret = ip_route_get(ip_str, "src", &loc);
+       if (ret != KNOT_EOK) {
+               return ret;
        }
-       pclose(p);
+       ret = (inet_pton(ipv6 ? AF_INET6 : AF_INET, loc, local) <= 0 ? KNOT_EMALF : KNOT_EOK);
+       free(loc);
+
        return ret;
 }
 
@@ -420,7 +446,7 @@ int main(int argc, char *argv[])
                usleep(10000);
 
                char dev1[IFNAMSIZ], dev2[IFNAMSIZ];
-               ret = remoteIP2MAC(argv[3], ctx.ipv6, dev1, ctx.target_mac);
+               ret = distantIP2MAC(argv[3], ctx.ipv6, dev1, ctx.target_mac);
                if (ret != KNOT_EOK) {
                        printf("can't get remote MAC of `%s` by ARP query: %s\n", argv[3], knot_strerror(ret));
                        goto pusage;