From 3dc4e7e08dfb7571cfc1cd8a4f5fef47773d231d Mon Sep 17 00:00:00 2001
From: "Ricardo (XenGi) Band" <email@ricardo.band>
Date: Fri, 7 Aug 2026 17:09:45 +0200
Subject: [PATCH] fix

---
 mdns-repeater.c | 39 +++++++++++++++++++++++++++------------
 1 file changed, 27 insertions(+), 12 deletions(-)

diff --git a/mdns-repeater.c b/mdns-repeater.c
index 58a70e3..64d87cc 100644
--- a/mdns-repeater.c
+++ b/mdns-repeater.c
@@ -138,7 +138,9 @@ static int setup_sockopts(int fd, int arr_idx, int sys_ifindex, int af) {
     if (af == AF_INET) {
         if (setsockopt(fd, IPPROTO_IP, IP_MULTICAST_LOOP, &off, sizeof(off)) < 0)
             perror("IP_MULTICAST_LOOP");
-        if (setsockopt(fd, IPPROTO_IP, IP_MULTICAST_IF, &sys_ifindex, sizeof(sys_ifindex)) < 0)
+        struct ip_mreqn mreq_if = {0};
+        mreq_if.imr_ifindex = sys_ifindex;
+        if (setsockopt(fd, IPPROTO_IP, IP_MULTICAST_IF, &mreq_if, sizeof(mreq_if)) < 0)
             perror("IP_MULTICAST_IF");
     } else {
         if (setsockopt(fd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &off, sizeof(off)) < 0)
@@ -205,6 +207,19 @@ static void repeat(const char *buf, int len, int src_idx, int af) {
     msg.msg_iov     = iov;
     msg.msg_iovlen  = 1;
 
+    struct sockaddr_in  dst4  = {0};
+    struct sockaddr_in6 dst6  = {0};
+    struct sockaddr    *dstop = NULL;
+    socklen_t           dstlen = 0;
+
+    dst4.sin_family = AF_INET;
+    dst4.sin_port   = htons(MDNS_PORT);
+    inet_pton(AF_INET, MDNS_GROUP_IP, &dst4.sin_addr);
+
+    dst6.sin6_family   = AF_INET6;
+    dst6.sin6_port     = htons(MDNS_PORT);
+    inet_pton(AF_INET6, MDNS_GROUP_IP6, &dst6.sin6_addr);
+
     for (int i = 0; i < n_ifaces; i++) {
         if (i == src_idx) continue;
 
@@ -214,7 +229,10 @@ static void repeat(const char *buf, int len, int src_idx, int af) {
         if (af == AF_INET) {
             struct in_pktinfo pktinfo = {0};
             pktinfo.ipi_ifindex = ifaces[i].index;
-            inet_pton(AF_INET, MDNS_GROUP_IP, &pktinfo.ipi_spec_dst);
+            pktinfo.ipi_spec_dst.s_addr = INADDR_ANY;
+
+            dstop  = (struct sockaddr *)&dst4;
+            dstlen = sizeof(dst4);
 
             msg.msg_control    = cmsg_buf;
             msg.msg_controllen = sizeof(cmsg_buf);
@@ -225,22 +243,19 @@ static void repeat(const char *buf, int len, int src_idx, int af) {
             cmsg->cmsg_len   = CMSG_LEN(sizeof(struct in_pktinfo));
             memcpy(CMSG_DATA(cmsg), &pktinfo, sizeof(pktinfo));
             msg.msg_controllen = cmsg->cmsg_len;
-
-            msg.msg_name    = NULL;
-            msg.msg_namelen = 0;
         } else {
-            struct sockaddr_in6 dst = {0};
-            dst.sin6_family   = AF_INET6;
-            dst.sin6_port     = htons(MDNS_PORT);
-            inet_pton(AF_INET6, MDNS_GROUP_IP6, &dst.sin6_addr);
-            dst.sin6_scope_id = ifaces[i].index;
+            dst6.sin6_scope_id = ifaces[i].index;
+
+            dstop  = (struct sockaddr *)&dst6;
+            dstlen = sizeof(dst6);
 
-            msg.msg_name    = &dst;
-            msg.msg_namelen = sizeof(dst);
             msg.msg_control    = NULL;
             msg.msg_controllen = 0;
         }
 
+        msg.msg_name    = dstop;
+        msg.msg_namelen = dstlen;
+
         ssize_t sent = sendmsg(fd, &msg, 0);
         if (sent < 0 && errno != EAGAIN && errno != EWOULDBLOCK) {
             fprintf(stderr, "sendmsg(%s): %s\n", ifaces[i].name, strerror(errno));