interface: ask for unicast responses by default

When able to bind the socket without REUSEPORT, unicast responses can
be received on the main port. Indicate that in outgoing questions in order
to reduce unnecessary multicast traffic.

Signed-off-by: Felix Fietkau <[email protected]>

diff --git a/dns.c b/dns.c
index 7c24ddc8be4de9bbeefbaad87cc7e80d0c57d2bd..18210f177a11ef517952ee298eef1111dbe4f1a5 100644 (file)
--- a/dns.c
+++ b/dns.c
@@ -185,7 +185,7 @@ void dns_packet_send(struct interface *iface, struct sockaddr *to, bool query, i
 
        if (query) {
                if (multicast < 0)
-                       multicast = interface_multicast(iface);
+                       multicast = iface->need_multicast;
 
                for (i = 0; i < pkt_n_q; i++)
                        dns_question_set_multicast(pkt_q[i], multicast);

diff --git a/interface.c b/interface.c
index 944666f1b0a058c6cd924751f9b477a0bf17de2a..e2f0ce9a4e1c2ea65199b419b851fc09a2d2e24d 100644 (file)
--- a/interface.c
+++ b/interface.c
@@ -478,7 +478,7 @@ iface_update_cb(struct vlist_tree *tree, struct vlist_node *node_new,
                interface_start(if_new);
 }
 
-static int interface_init_socket(enum umdns_socket_type type)
+static int interface_init_socket(enum umdns_socket_type type, bool *mcast)
 {
        struct sockaddr_in6 local6 = {
                .sin6_family = AF_INET6
@@ -492,6 +492,7 @@ static int interface_init_socket(enum umdns_socket_type type)
        int no = 0;
        int fd;
        int af = (type & SOCKTYPE_BIT_IPV6) ? AF_INET6 : AF_INET;
+       bool reuseport = false;
 
        if (ufd[type].fd >= 0)
                return 0;
@@ -501,9 +502,6 @@ static int interface_init_socket(enum umdns_socket_type type)
                return -1;
 
        setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes));
-#ifdef SO_REUSEPORT
-       setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &yes, sizeof(yes));
-#endif
 
        switch (type) {
        case SOCK_UC_IPV4:
@@ -524,6 +522,7 @@ static int interface_init_socket(enum umdns_socket_type type)
                break;
        }
 
+retry:
        if (type & SOCKTYPE_BIT_IPV6) {
                ufd[type].cb = read_socket6;
                if (bind(fd, (struct sockaddr *)&local6, sizeof(local6)) < 0)
@@ -545,6 +544,14 @@ static int interface_init_socket(enum umdns_socket_type type)
        return 0;
 
 error:
+       if (!reuseport) {
+#ifdef SO_REUSEPORT
+               setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &yes, sizeof(yes));
+#endif
+               reuseport = true;
+               *mcast = true;
+               goto retry;
+       }
        close(ufd[type].fd);
        return -1;
 }
@@ -555,9 +562,10 @@ __interface_add(const char *name, enum umdns_socket_type type,
 {
        struct interface *iface;
        unsigned int ifindex;
+       bool mcast = false;
        char *id_buf;
 
-       if (interface_init_socket(type))
+       if (interface_init_socket(type, &mcast))
                goto error;
 
        ifindex = if_nametoindex(name);
@@ -572,6 +580,7 @@ __interface_add(const char *name, enum umdns_socket_type type,
        iface->ifindex = ifindex;
        iface->type = type;
        iface->addrs = *list;
+       iface->need_multicast = mcast;
 
        vlist_add(&interfaces, &iface->node, id_buf);
        return;

diff --git a/interface.h b/interface.h
index aca2f41a31fe1d663ebe64ec8eb83a734bfa6d68..0c37736aee4d871e1bab2f97d9bf799133d586c3 100644 (file)
--- a/interface.h
+++ b/interface.h
@@ -52,6 +52,7 @@ struct interface {
 
        const char *name;
        enum umdns_socket_type type;
+       bool need_multicast;
        int ifindex;
 
        struct interface_addr_list addrs;