diff --git a/src/basic/socket-util.c b/src/basic/socket-util.c
index 07f534f34d..5218374b2b 100644
--- a/src/basic/socket-util.c
+++ b/src/basic/socket-util.c
@@ -1130,6 +1130,7 @@ int socket_bind_to_ifname(int fd, const char *ifname) {
 
 int socket_bind_to_ifindex(int fd, int ifindex) {
         char ifname[IF_NAMESIZE + 1];
+        int r;
 
         assert(fd >= 0);
 
@@ -1141,10 +1142,9 @@ int socket_bind_to_ifindex(int fd, int ifindex) {
                 return 0;
         }
 
-        if (setsockopt(fd, SOL_SOCKET, SO_BINDTOIFINDEX, &ifindex, sizeof(ifindex)) >= 0)
-                return 0;
-        if (errno != ENOPROTOOPT)
-                return -errno;
+        r = setsockopt_int(fd, SOL_SOCKET, SO_BINDTOIFINDEX, ifindex);
+        if (r != -ENOPROTOOPT)
+                return r;
 
         /* Fall back to SO_BINDTODEVICE on kernels < 5.0 which didn't have SO_BINDTOIFINDEX */
         if (!format_ifname(ifindex, ifname))
diff --git a/src/libsystemd-network/dhcp6-internal.h b/src/libsystemd-network/dhcp6-internal.h
index b0d1216eed..baf7bb2ef4 100644
--- a/src/libsystemd-network/dhcp6-internal.h
+++ b/src/libsystemd-network/dhcp6-internal.h
@@ -112,7 +112,7 @@ int dhcp6_option_parse_ip6addrs(uint8_t *optval, uint16_t optlen,
 int dhcp6_option_parse_domainname(const uint8_t *optval, uint16_t optlen,
                                   char ***str_arr);
 
-int dhcp6_network_bind_udp_socket(int index, struct in6_addr *address);
+int dhcp6_network_bind_udp_socket(int ifindex, struct in6_addr *address);
 int dhcp6_network_send_udp_socket(int s, struct in6_addr *address,
                                   const void *packet, size_t len);
 
diff --git a/src/libsystemd-network/dhcp6-network.c b/src/libsystemd-network/dhcp6-network.c
index f82afe6a09..e2efa8bbe3 100644
--- a/src/libsystemd-network/dhcp6-network.c
+++ b/src/libsystemd-network/dhcp6-network.c
@@ -17,16 +17,16 @@
 #include "fd-util.h"
 #include "socket-util.h"
 
-int dhcp6_network_bind_udp_socket(int index, struct in6_addr *local_address) {
+int dhcp6_network_bind_udp_socket(int ifindex, struct in6_addr *local_address) {
         union sockaddr_union src = {
                 .in6.sin6_family = AF_INET6,
                 .in6.sin6_port = htobe16(DHCP6_PORT_CLIENT),
-                .in6.sin6_scope_id = index,
+                .in6.sin6_scope_id = ifindex,
         };
         _cleanup_close_ int s = -1;
         int r;
 
-        assert(index > 0);
+        assert(ifindex > 0);
         assert(local_address);
 
         src.in6.sin6_addr = *local_address;
diff --git a/src/libsystemd-network/icmp6-util.c b/src/libsystemd-network/icmp6-util.c
index bdd94867ac..d9690293f1 100644
--- a/src/libsystemd-network/icmp6-util.c
+++ b/src/libsystemd-network/icmp6-util.c
@@ -81,11 +81,11 @@ static int icmp6_bind_router_message(const struct icmp6_filter *filter,
         return TAKE_FD(s);
 }
 
-int icmp6_bind_router_solicitation(int index) {
+int icmp6_bind_router_solicitation(int ifindex) {
         struct icmp6_filter filter = {};
         struct ipv6_mreq mreq = {
                 .ipv6mr_multiaddr = IN6ADDR_ALL_NODES_MULTICAST_INIT,
-                .ipv6mr_interface = index,
+                .ipv6mr_interface = ifindex,
         };
 
         ICMP6_FILTER_SETBLOCKALL(&filter);
@@ -94,11 +94,11 @@ int icmp6_bind_router_solicitation(int index) {
         return icmp6_bind_router_message(&filter, &mreq);
 }
 
-int icmp6_bind_router_advertisement(int index) {
+int icmp6_bind_router_advertisement(int ifindex) {
         struct icmp6_filter filter = {};
         struct ipv6_mreq mreq = {
                 .ipv6mr_multiaddr = IN6ADDR_ALL_ROUTERS_MULTICAST_INIT,
-                .ipv6mr_interface = index,
+                .ipv6mr_interface = ifindex,
         };
 
         ICMP6_FILTER_SETBLOCKALL(&filter);
diff --git a/src/libsystemd-network/icmp6-util.h b/src/libsystemd-network/icmp6-util.h
index 725a68086b..ac68ded1fe 100644
--- a/src/libsystemd-network/icmp6-util.h
+++ b/src/libsystemd-network/icmp6-util.h
@@ -17,8 +17,8 @@
         { { { 0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, \
               0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01 } } }
 
-int icmp6_bind_router_solicitation(int index);
-int icmp6_bind_router_advertisement(int index);
+int icmp6_bind_router_solicitation(int ifindex);
+int icmp6_bind_router_advertisement(int ifindex);
 int icmp6_send_router_solicitation(int s, const struct ether_addr *ether_addr);
 int icmp6_receive(int fd, void *buffer, size_t size, struct in6_addr *dst,
                   triple_timestamp *timestamp);
diff --git a/src/libsystemd-network/sd-dhcp6-client.c b/src/libsystemd-network/sd-dhcp6-client.c
index e1572703e2..7a8823cce9 100644
--- a/src/libsystemd-network/sd-dhcp6-client.c
+++ b/src/libsystemd-network/sd-dhcp6-client.c
@@ -159,7 +159,7 @@ int sd_dhcp6_client_set_callback(
 int sd_dhcp6_client_set_ifindex(sd_dhcp6_client *client, int ifindex) {
 
         assert_return(client, -EINVAL);
-        assert_return(ifindex >= -1, -EINVAL);
+        assert_return(ifindex > 0, -EINVAL);
         assert_return(IN_SET(client->state, DHCP6_STATE_STOPPED), -EBUSY);
 
         client->ifindex = ifindex;
diff --git a/src/libsystemd-network/sd-radv.c b/src/libsystemd-network/sd-radv.c
index 7ea6f0d561..cc5c0223b5 100644
--- a/src/libsystemd-network/sd-radv.c
+++ b/src/libsystemd-network/sd-radv.c
@@ -415,7 +415,7 @@ _public_ int sd_radv_start(sd_radv *ra) {
 
 _public_ int sd_radv_set_ifindex(sd_radv *ra, int ifindex) {
         assert_return(ra, -EINVAL);
-        assert_return(ifindex >= -1, -EINVAL);
+        assert_return(ifindex > 0, -EINVAL);
 
         if (ra->state != SD_RADV_STATE_IDLE)
                 return -EBUSY;
diff --git a/src/libsystemd-network/test-dhcp-client.c b/src/libsystemd-network/test-dhcp-client.c
index 80a8566194..8f2f4462be 100644
--- a/src/libsystemd-network/test-dhcp-client.c
+++ b/src/libsystemd-network/test-dhcp-client.c
@@ -258,7 +258,7 @@ int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link, const
 }
 
 int dhcp_network_bind_raw_socket(
-                int index,
+                int ifindex,
                 union sockaddr_union *link,
                 uint32_t id,
                 const uint8_t *addr, size_t addr_len,
diff --git a/src/libsystemd-network/test-dhcp6-client.c b/src/libsystemd-network/test-dhcp6-client.c
index 56c8c978e5..7af7d670b5 100644
--- a/src/libsystemd-network/test-dhcp6-client.c
+++ b/src/libsystemd-network/test-dhcp6-client.c
@@ -30,7 +30,7 @@ static struct ether_addr mac_addr = {
 
 static sd_event_source *hangcheck;
 static int test_dhcp_fd[2];
-static int test_index = 42;
+static int test_ifindex = 42;
 static int test_client_message_num;
 static be32_t test_iaid = 0;
 static uint8_t test_duid[14] = { };
@@ -48,7 +48,7 @@ static int test_client_basic(sd_event *e) {
 
         assert_se(sd_dhcp6_client_set_ifindex(client, 15) == 0);
         assert_se(sd_dhcp6_client_set_ifindex(client, -42) == -EINVAL);
-        assert_se(sd_dhcp6_client_set_ifindex(client, -1) == 0);
+        assert_se(sd_dhcp6_client_set_ifindex(client, -1) == -EINVAL);
         assert_se(sd_dhcp6_client_set_ifindex(client, 42) >= 0);
 
         assert_se(sd_dhcp6_client_set_mac(client, (const uint8_t *) &mac_addr,
@@ -877,8 +877,8 @@ int dhcp6_network_send_udp_socket(int s, struct in6_addr *server_address,
         return len;
 }
 
-int dhcp6_network_bind_udp_socket(int index, struct in6_addr *local_address) {
-        assert_se(index == test_index);
+int dhcp6_network_bind_udp_socket(int ifindex, struct in6_addr *local_address) {
+        assert_se(ifindex == test_ifindex);
 
         if (socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0, test_dhcp_fd) < 0)
                 return -errno;
@@ -899,7 +899,7 @@ static int test_client_solicit(sd_event *e) {
 
         assert_se(sd_dhcp6_client_attach_event(client, e, 0) >= 0);
 
-        assert_se(sd_dhcp6_client_set_ifindex(client, test_index) == 0);
+        assert_se(sd_dhcp6_client_set_ifindex(client, test_ifindex) == 0);
         assert_se(sd_dhcp6_client_set_mac(client, (const uint8_t *) &mac_addr,
                                           sizeof (mac_addr),
                                           ARPHRD_ETHER) >= 0);
diff --git a/src/libsystemd-network/test-ipv4ll.c b/src/libsystemd-network/test-ipv4ll.c
index 6051e65820..310b658e18 100644
--- a/src/libsystemd-network/test-ipv4ll.c
+++ b/src/libsystemd-network/test-ipv4ll.c
@@ -78,7 +78,7 @@ int arp_send_announcement(int fd, int ifindex,
         return arp_network_send_raw_socket(fd, ifindex, &ea);
 }
 
-int arp_network_bind_raw_socket(int index, be32_t address, const struct ether_addr *eth_mac) {
+int arp_network_bind_raw_socket(int ifindex, be32_t address, const struct ether_addr *eth_mac) {
         if (socketpair(AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0, test_fd) < 0)
                 return -errno;
 
diff --git a/src/libsystemd-network/test-ndisc-ra.c b/src/libsystemd-network/test-ndisc-ra.c
index 7c6c4663f3..d759ec03a8 100644
--- a/src/libsystemd-network/test-ndisc-ra.c
+++ b/src/libsystemd-network/test-ndisc-ra.c
@@ -159,8 +159,8 @@ static void test_radv(void) {
         assert_se(ra);
 
         assert_se(sd_radv_set_ifindex(NULL, 0) < 0);
-        assert_se(sd_radv_set_ifindex(ra, 0) >= 0);
-        assert_se(sd_radv_set_ifindex(ra, -1) >= 0);
+        assert_se(sd_radv_set_ifindex(ra, 0) < 0);
+        assert_se(sd_radv_set_ifindex(ra, -1) < 0);
         assert_se(sd_radv_set_ifindex(ra, -2) < 0);
         assert_se(sd_radv_set_ifindex(ra, 42) >= 0);
 
@@ -219,12 +219,12 @@ static void test_radv(void) {
         assert_se(!ra);
 }
 
-int icmp6_bind_router_solicitation(int index) {
+int icmp6_bind_router_solicitation(int ifindex) {
         return -ENOSYS;
 }
 
-int icmp6_bind_router_advertisement(int index) {
-        assert_se(index == 42);
+int icmp6_bind_router_advertisement(int ifindex) {
+        assert_se(ifindex == 42);
 
         return test_fd[1];
 }
diff --git a/src/libsystemd-network/test-ndisc-rs.c b/src/libsystemd-network/test-ndisc-rs.c
index 9fc902645c..5d1e66fcdc 100644
--- a/src/libsystemd-network/test-ndisc-rs.c
+++ b/src/libsystemd-network/test-ndisc-rs.c
@@ -174,8 +174,8 @@ static int test_rs_hangcheck(sd_event_source *s, uint64_t usec,
         return 0;
 }
 
-int icmp6_bind_router_solicitation(int index) {
-        assert_se(index == 42);
+int icmp6_bind_router_solicitation(int ifindex) {
+        assert_se(ifindex == 42);
 
         if (socketpair(AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0, test_fd) < 0)
                 return -errno;
@@ -183,8 +183,7 @@ int icmp6_bind_router_solicitation(int index) {
         return test_fd[0];
 }
 
-int icmp6_bind_router_advertisement(int index) {
-
+int icmp6_bind_router_advertisement(int ifindex) {
         return -ENOSYS;
 }
 
diff --git a/src/resolve/resolved-dns-stream.c b/src/resolve/resolved-dns-stream.c
index 1e2ff05c3e..d4c49e673e 100644
--- a/src/resolve/resolved-dns-stream.c
+++ b/src/resolve/resolved-dns-stream.c
@@ -190,7 +190,7 @@ static int dns_stream_identify(DnsStream *s) {
                 s->ifindex = manager_find_ifindex(s->manager, s->local.sa.sa_family, s->local.sa.sa_family == AF_INET ? (union in_addr_union*) &s->local.in.sin_addr : (union in_addr_union*)  &s->local.in6.sin6_addr);
 
         if (s->protocol == DNS_PROTOCOL_LLMNR && s->ifindex > 0) {
-                uint32_t ifindex = htobe32(s->ifindex);
+                be32_t ifindex = htobe32(s->ifindex);
 
                 /* Make sure all packets for this connection are sent on the same interface */
                 if (s->local.sa.sa_family == AF_INET) {