Merge pull request #31440 from yuwata/sd-ndisc-sd-radv-cleanups

sd-ndisc,sd-radv: several trivial cleanups

src/libsystemd-network/icmp6-util-unix.c

@@ -16,15 +16,11 @@ static struct in6_addr dummy_link_local = {
         },
 };
 
-int icmp6_bind_router_solicitation(int ifindex) {
-        if (socketpair(AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0, test_fd) < 0)
+int icmp6_bind(int ifindex, bool is_router) {
+        if (!is_router && socketpair(AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0, test_fd) < 0)
                 return -errno;
 
-        return test_fd[0];
-}
-
-int icmp6_bind_router_advertisement(int ifindex) {
-        return test_fd[1];
+        return test_fd[is_router];
 }
 
 int icmp6_send_router_solicitation(int s, const struct ether_addr *ether_addr) {

src/libsystemd-network/icmp6-util.c

@@ -21,37 +21,42 @@
 #include "network-common.h"
 #include "socket-util.h"
 
-#define IN6ADDR_ALL_ROUTERS_MULTICAST_INIT \
-        { { { 0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, \
-              0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02 } } }
-
-#define IN6ADDR_ALL_NODES_MULTICAST_INIT \
-        { { { 0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, \
-              0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01 } } }
-
-static int icmp6_bind_router_message(const struct icmp6_filter *filter,
-                                     const struct ipv6_mreq *mreq) {
-        int ifindex = mreq->ipv6mr_interface;
+int icmp6_bind(int ifindex, bool is_router) {
+        struct icmp6_filter filter = {};
+        struct ipv6_mreq mreq;
         _cleanup_close_ int s = -EBADF;
         int r;
 
-        assert(filter);
-        assert(mreq);
+        assert(ifindex > 0);
+
+        ICMP6_FILTER_SETBLOCKALL(&filter);
+        if (is_router) {
+                mreq = (struct ipv6_mreq) {
+                        .ipv6mr_multiaddr = IN6ADDR_ALL_ROUTERS_MULTICAST_INIT,
+                        .ipv6mr_interface = ifindex,
+                };
+                ICMP6_FILTER_SETPASS(ND_ROUTER_SOLICIT, &filter);
+        } else {
+                mreq = (struct ipv6_mreq) {
+                        .ipv6mr_multiaddr = IN6ADDR_ALL_NODES_MULTICAST_INIT,
+                        .ipv6mr_interface = ifindex,
+                };
+                ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filter);
+        }
 
         s = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC | SOCK_NONBLOCK, IPPROTO_ICMPV6);
         if (s < 0)
                 return -errno;
 
-        if (setsockopt(s, IPPROTO_ICMPV6, ICMP6_FILTER, filter, sizeof(*filter)) < 0)
+        if (setsockopt(s, IPPROTO_ICMPV6, ICMP6_FILTER, &filter, sizeof(filter)) < 0)
                 return -errno;
 
-        if (setsockopt(s, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, mreq, sizeof(*mreq)) < 0)
+        if (setsockopt(s, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0)
                 return -errno;
 
-        /* RFC 3315, section 6.7, bullet point 2 may indicate that an
-           IPV6_PKTINFO socket option also applies for ICMPv6 multicast.
-           Empirical experiments indicates otherwise and therefore an
-           IPV6_MULTICAST_IF socket option is used here instead */
+        /* RFC 3315, section 6.7, bullet point 2 may indicate that an IPV6_PKTINFO socket option also applies
+         * for ICMPv6 multicast. Empirical experiments indicates otherwise and therefore an IPV6_MULTICAST_IF
+         * socket option is used here instead. */
         r = setsockopt_int(s, IPPROTO_IPV6, IPV6_MULTICAST_IF, ifindex);
         if (r < 0)
                 return r;
@@ -83,32 +88,6 @@ static int icmp6_bind_router_message(const struct icmp6_filter *filter,
         return TAKE_FD(s);
 }
 
-int icmp6_bind_router_solicitation(int ifindex) {
-        struct icmp6_filter filter = {};
-        struct ipv6_mreq mreq = {
-                .ipv6mr_multiaddr = IN6ADDR_ALL_NODES_MULTICAST_INIT,
-                .ipv6mr_interface = ifindex,
-        };
-
-        ICMP6_FILTER_SETBLOCKALL(&filter);
-        ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filter);
-
-        return icmp6_bind_router_message(&filter, &mreq);
-}
-
-int icmp6_bind_router_advertisement(int ifindex) {
-        struct icmp6_filter filter = {};
-        struct ipv6_mreq mreq = {
-                .ipv6mr_multiaddr = IN6ADDR_ALL_ROUTERS_MULTICAST_INIT,
-                .ipv6mr_interface = ifindex,
-        };
-
-        ICMP6_FILTER_SETBLOCKALL(&filter);
-        ICMP6_FILTER_SETPASS(ND_ROUTER_SOLICIT, &filter);
-
-        return icmp6_bind_router_message(&filter, &mreq);
-}
-
 int icmp6_send_router_solicitation(int s, const struct ether_addr *ether_addr) {
         struct sockaddr_in6 dst = {
                 .sin6_family = AF_INET6,

src/libsystemd-network/icmp6-util.h

@@ -6,6 +6,7 @@
 ***/
 
 #include <net/ethernet.h>
+#include <stdbool.h>
 
 #include "time-util.h"
 
@@ -17,8 +18,7 @@
         { { { 0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, \
               0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01 } } }
 
-int icmp6_bind_router_solicitation(int ifindex);
-int icmp6_bind_router_advertisement(int ifindex);
+int icmp6_bind(int ifindex, bool is_router);
 int icmp6_send_router_solicitation(int s, const struct ether_addr *ether_addr);
 int icmp6_receive(
                 int fd,

src/libsystemd-network/sd-ndisc.c

@@ -234,19 +234,19 @@ static int ndisc_recv(sd_event_source *s, int fd, uint32_t revents, void *userda
         if (r < 0)
                 switch (r) {
                 case -EADDRNOTAVAIL:
-                        log_ndisc(nd, "Received RA from neither link-local nor null address. Ignoring.");
+                        log_ndisc(nd, "Received an ICMPv6 packet from neither link-local nor null address, ignoring.");
                         return 0;
 
                 case -EMULTIHOP:
-                        log_ndisc(nd, "Received RA with invalid hop limit. Ignoring.");
+                        log_ndisc(nd, "Received an ICMPv6 packet with an invalid hop limit, ignoring.");
                         return 0;
 
                 case -EPFNOSUPPORT:
-                        log_ndisc(nd, "Received invalid source address from ICMPv6 socket. Ignoring.");
+                        log_ndisc(nd, "Received an ICMPv6 packet with an invalid source address, ignoring.");
                         return 0;
 
                 default:
-                        log_ndisc_errno(nd, r, "Unexpected error while reading from ICMPv6, ignoring: %m");
+                        log_ndisc_errno(nd, r, "Unexpected error while receiving an ICMPv6 packet, ignoring: %m");
                         return 0;
                 }
 
@@ -335,9 +335,61 @@ int sd_ndisc_stop(sd_ndisc *nd) {
         return 1;
 }
 
+static int ndisc_setup_recv_event(sd_ndisc *nd) {
+        int r;
+
+        assert(nd);
+        assert(nd->event);
+        assert(nd->ifindex > 0);
+
+        _cleanup_close_ int fd = -EBADF;
+        fd = icmp6_bind(nd->ifindex, /* is_router = */ false);
+        if (fd < 0)
+                return fd;
+
+        _cleanup_(sd_event_source_unrefp) sd_event_source *s = NULL;
+        r = sd_event_add_io(nd->event, &s, fd, EPOLLIN, ndisc_recv, nd);
+        if (r < 0)
+                return r;
+
+        r = sd_event_source_set_priority(s, nd->event_priority);
+        if (r < 0)
+                return r;
+
+        (void) sd_event_source_set_description(s, "ndisc-receive-router-message");
+
+        nd->fd = TAKE_FD(fd);
+        nd->recv_event_source = TAKE_PTR(s);
+        return 1;
+}
+
+static int ndisc_setup_timer(sd_ndisc *nd) {
+        int r;
+
+        assert(nd);
+        assert(nd->event);
+
+        r = event_reset_time_relative(nd->event, &nd->timeout_event_source,
+                                      CLOCK_BOOTTIME,
+                                      USEC_PER_SEC / 2, 1 * USEC_PER_SEC, /* See RFC 8415 sec. 18.2.1 */
+                                      ndisc_timeout, nd,
+                                      nd->event_priority, "ndisc-timeout", true);
+        if (r < 0)
+                return r;
+
+        r = event_reset_time_relative(nd->event, &nd->timeout_no_ra,
+                                      CLOCK_BOOTTIME,
+                                      NDISC_TIMEOUT_NO_RA_USEC, 10 * USEC_PER_MSEC,
+                                      ndisc_timeout_no_ra, nd,
+                                      nd->event_priority, "ndisc-timeout-no-ra", true);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
 int sd_ndisc_start(sd_ndisc *nd) {
         int r;
-        usec_t time_now;
 
         assert_return(nd, -EINVAL);
         assert_return(nd->event, -EINVAL);
@@ -346,39 +398,11 @@ int sd_ndisc_start(sd_ndisc *nd) {
         if (sd_ndisc_is_running(nd))
                 return 0;
 
-        assert(!nd->recv_event_source);
-
-        r = sd_event_now(nd->event, CLOCK_BOOTTIME, &time_now);
+        r = ndisc_setup_recv_event(nd);
         if (r < 0)
                 goto fail;
 
-        nd->fd = icmp6_bind_router_solicitation(nd->ifindex);
-        if (nd->fd < 0)
-                return nd->fd;
-
-        r = sd_event_add_io(nd->event, &nd->recv_event_source, nd->fd, EPOLLIN, ndisc_recv, nd);
-        if (r < 0)
-                goto fail;
-
-        r = sd_event_source_set_priority(nd->recv_event_source, nd->event_priority);
-        if (r < 0)
-                goto fail;
-
-        (void) sd_event_source_set_description(nd->recv_event_source, "ndisc-receive-message");
-
-        r = event_reset_time(nd->event, &nd->timeout_event_source,
-                             CLOCK_BOOTTIME,
-                             time_now + USEC_PER_SEC / 2, 1 * USEC_PER_SEC, /* See RFC 8415 sec. 18.2.1 */
-                             ndisc_timeout, nd,
-                             nd->event_priority, "ndisc-timeout", true);
-        if (r < 0)
-                goto fail;
-
-        r = event_reset_time(nd->event, &nd->timeout_no_ra,
-                             CLOCK_BOOTTIME,
-                             time_now + NDISC_TIMEOUT_NO_RA_USEC, 10 * USEC_PER_MSEC,
-                             ndisc_timeout_no_ra, nd,
-                             nd->event_priority, "ndisc-timeout-no-ra", true);
+        r = ndisc_setup_timer(nd);
         if (r < 0)
                 goto fail;
 

src/libsystemd-network/sd-radv.c

@@ -121,30 +121,39 @@ static sd_radv *radv_free(sd_radv *ra) {
 DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(sd_radv, sd_radv, radv_free);
 
 static bool router_lifetime_is_valid(usec_t lifetime_usec) {
+        assert_cc(RADV_MAX_ROUTER_LIFETIME_USEC <= UINT16_MAX * USEC_PER_SEC);
         return lifetime_usec == 0 ||
                 (lifetime_usec >= RADV_MIN_ROUTER_LIFETIME_USEC &&
                  lifetime_usec <= RADV_MAX_ROUTER_LIFETIME_USEC);
 }
 
-static int radv_send(sd_radv *ra, const struct in6_addr *dst, usec_t lifetime_usec) {
+static int radv_send_router(sd_radv *ra, const struct in6_addr *dst, usec_t lifetime_usec) {
+        assert(ra);
+        assert(router_lifetime_is_valid(lifetime_usec));
+
         struct sockaddr_in6 dst_addr = {
                 .sin6_family = AF_INET6,
                 .sin6_addr = IN6ADDR_ALL_NODES_MULTICAST_INIT,
         };
-        struct nd_router_advert adv = {};
+        struct nd_router_advert adv = {
+                .nd_ra_type = ND_ROUTER_ADVERT,
+                .nd_ra_router_lifetime = usec_to_be16_sec(lifetime_usec),
+                .nd_ra_retransmit = usec_to_be32_msec(ra->retransmit_usec),
+        };
         struct {
                 struct nd_opt_hdr opthdr;
                 struct ether_addr slladdr;
         } _packed_ opt_mac = {
                 .opthdr = {
                         .nd_opt_type = ND_OPT_SOURCE_LINKADDR,
-                        .nd_opt_len = (sizeof(struct nd_opt_hdr) +
-                                       sizeof(struct ether_addr) - 1) /8 + 1,
+                        .nd_opt_len = DIV_ROUND_UP(sizeof(struct nd_opt_hdr) + sizeof(struct ether_addr), 8),
                 },
+                .slladdr = ra->mac_addr,
         };
         struct nd_opt_mtu opt_mtu =  {
                 .nd_opt_mtu_type = ND_OPT_MTU,
                 .nd_opt_mtu_len = 1,
+                .nd_opt_mtu_mtu = htobe32(ra->mtu),
         };
         /* Reserve iov space for RA header, linkaddr, MTU, N prefixes, N routes, N pref64 prefixes, RDNSS,
          * DNSSL, and home agent. */
@@ -157,9 +166,6 @@ static int radv_send(sd_radv *ra, const struct in6_addr *dst, usec_t lifetime_us
         usec_t time_now;
         int r;
 
-        assert(ra);
-        assert(router_lifetime_is_valid(lifetime_usec));
-
         r = sd_event_now(ra->event, CLOCK_BOOTTIME, &time_now);
         if (r < 0)
                 return r;
@@ -167,25 +173,19 @@ static int radv_send(sd_radv *ra, const struct in6_addr *dst, usec_t lifetime_us
         if (dst && in6_addr_is_set(dst))
                 dst_addr.sin6_addr = *dst;
 
-        adv.nd_ra_type = ND_ROUTER_ADVERT;
+        /* The nd_ra_curhoplimit and nd_ra_flags_reserved fields cannot specified with nd_ra_router_lifetime
+         * simultaneously in the structured initializer in the above. */
         adv.nd_ra_curhoplimit = ra->hop_limit;
-        adv.nd_ra_retransmit = usec_to_be32_msec(ra->retransmit_usec);
         adv.nd_ra_flags_reserved = ra->flags;
-        assert_cc(RADV_MAX_ROUTER_LIFETIME_USEC <= UINT16_MAX * USEC_PER_SEC);
-        adv.nd_ra_router_lifetime = usec_to_be16_sec(lifetime_usec);
         iov[msg.msg_iovlen++] = IOVEC_MAKE(&adv, sizeof(adv));
 
-        /* MAC address is optional, either because the link does not use L2
-           addresses or load sharing is desired. See RFC 4861, Section 4.2 */
-        if (!ether_addr_is_null(&ra->mac_addr)) {
-                opt_mac.slladdr = ra->mac_addr;
+        /* MAC address is optional, either because the link does not use L2 addresses or load sharing is
+         * desired. See RFC 4861, Section 4.2. */
+        if (!ether_addr_is_null(&ra->mac_addr))
                 iov[msg.msg_iovlen++] = IOVEC_MAKE(&opt_mac, sizeof(opt_mac));
-        }
 
-        if (ra->mtu > 0) {
-                opt_mtu.nd_opt_mtu_mtu = htobe32(ra->mtu);
+        if (ra->mtu > 0)
                 iov[msg.msg_iovlen++] = IOVEC_MAKE(&opt_mtu, sizeof(opt_mtu));
-        }
 
         LIST_FOREACH(prefix, p, ra->prefixes) {
                 usec_t lifetime_valid_usec, lifetime_preferred_usec;
@@ -263,15 +263,15 @@ static int radv_recv(sd_event_source *s, int fd, uint32_t revents, void *userdat
         if (r < 0)
                 switch (r) {
                 case -EADDRNOTAVAIL:
-                        log_radv(ra, "Received RS from neither link-local nor null address. Ignoring");
+                        log_radv(ra, "Received RS from neither link-local nor null address, ignoring.");
                         return 0;
 
                 case -EMULTIHOP:
-                        log_radv(ra, "Received RS with invalid hop limit. Ignoring.");
+                        log_radv(ra, "Received RS with invalid hop limit, ignoring.");
                         return 0;
 
                 case -EPFNOSUPPORT:
-                        log_radv(ra, "Received invalid source address from ICMPv6 socket. Ignoring.");
+                        log_radv(ra, "Received invalid source address from ICMPv6 socket, ignoring.");
                         return 0;
 
                 default:
@@ -288,12 +288,11 @@ static int radv_recv(sd_event_source *s, int fd, uint32_t revents, void *userdat
          * address option. See RFC 4861 Section 6.1.1. */
 
         const char *addr = IN6_ADDR_TO_STRING(&src);
-
-        r = radv_send(ra, &src, ra->lifetime_usec);
+        r = radv_send_router(ra, &src, ra->lifetime_usec);
         if (r < 0)
                 log_radv_errno(ra, r, "Unable to send solicited Router Advertisement to %s, ignoring: %m", addr);
         else
-                log_radv(ra, "Sent solicited Router Advertisement to %s", addr);
+                log_radv(ra, "Sent solicited Router Advertisement to %s.", addr);
 
         return 0;
 }
@@ -311,7 +310,7 @@ static int radv_timeout(sd_event_source *s, uint64_t usec, void *userdata) {
         if (r < 0)
                 goto fail;
 
-        r = radv_send(ra, NULL, ra->lifetime_usec);
+        r = radv_send_router(ra, NULL, ra->lifetime_usec);
         if (r < 0)
                 log_radv_errno(ra, r, "Unable to send Router Advertisement, ignoring: %m");
 
@@ -371,9 +370,10 @@ int sd_radv_stop(sd_radv *ra) {
 
         log_radv(ra, "Stopping IPv6 Router Advertisement daemon");
 
-        /* RFC 4861, Section 6.2.5, send at least one Router Advertisement
-           with zero lifetime  */
-        r = radv_send(ra, NULL, 0);
+        /* RFC 4861, Section 6.2.5:
+         * the router SHOULD transmit one or more (but not more than MAX_FINAL_RTR_ADVERTISEMENTS) final
+         * multicast Router Advertisements on the interface with a Router Lifetime field of zero. */
+        r = radv_send_router(ra, NULL, 0);
         if (r < 0)
                 log_radv_errno(ra, r, "Unable to send last Router Advertisement with router lifetime set to zero, ignoring: %m");
 
@@ -384,6 +384,34 @@ int sd_radv_stop(sd_radv *ra) {
         return 0;
 }
 
+static int radv_setup_recv_event(sd_radv *ra) {
+        int r;
+
+        assert(ra);
+        assert(ra->event);
+        assert(ra->ifindex > 0);
+
+        _cleanup_close_ int fd = -EBADF;
+        fd = icmp6_bind(ra->ifindex, /* is_router = */ true);
+        if (fd < 0)
+                return fd;
+
+        _cleanup_(sd_event_source_unrefp) sd_event_source *s = NULL;
+        r = sd_event_add_io(ra->event, &s, fd, EPOLLIN, radv_recv, ra);
+        if (r < 0)
+                return r;
+
+        r = sd_event_source_set_priority(s, ra->event_priority);
+        if (r < 0)
+                return r;
+
+        (void) sd_event_source_set_description(s, "radv-receive-message");
+
+        ra->fd = TAKE_FD(fd);
+        ra->recv_event_source = TAKE_PTR(s);
+        return 0;
+}
+
 int sd_radv_start(sd_radv *ra) {
         int r;
 
@@ -394,6 +422,10 @@ int sd_radv_start(sd_radv *ra) {
         if (ra->state != RADV_STATE_IDLE)
                 return 0;
 
+        r = radv_setup_recv_event(ra);
+        if (r < 0)
+                goto fail;
+
         r = event_reset_time(ra->event, &ra->timeout_event_source,
                              CLOCK_BOOTTIME,
                              0, 0,
@@ -402,22 +434,6 @@ int sd_radv_start(sd_radv *ra) {
         if (r < 0)
                 goto fail;
 
-        r = icmp6_bind_router_advertisement(ra->ifindex);
-        if (r < 0)
-                goto fail;
-
-        ra->fd = r;
-
-        r = sd_event_add_io(ra->event, &ra->recv_event_source, ra->fd, EPOLLIN, radv_recv, ra);
-        if (r < 0)
-                goto fail;
-
-        r = sd_event_source_set_priority(ra->recv_event_source, ra->event_priority);
-        if (r < 0)
-                goto fail;
-
-        (void) sd_event_source_set_description(ra->recv_event_source, "radv-receive-message");
-
         ra->state = RADV_STATE_ADVERTISING;
 
         log_radv(ra, "Started IPv6 Router Advertisement daemon");
@@ -674,7 +690,7 @@ int sd_radv_add_prefix(sd_radv *ra, sd_radv_prefix *p) {
                 return 0;
 
         /* If RAs have already been sent, send an RA immediately to announce the newly-added prefix */
-        r = radv_send(ra, NULL, ra->lifetime_usec);
+        r = radv_send_router(ra, NULL, ra->lifetime_usec);
         if (r < 0)
                 log_radv_errno(ra, r, "Unable to send Router Advertisement for added prefix %s, ignoring: %m", addr_p);
         else
@@ -770,7 +786,7 @@ int sd_radv_add_route_prefix(sd_radv *ra, sd_radv_route_prefix *p) {
                 return 0;
 
         /* If RAs have already been sent, send an RA immediately to announce the newly-added route prefix */
-        r = radv_send(ra, NULL, ra->lifetime_usec);
+        r = radv_send_router(ra, NULL, ra->lifetime_usec);
         if (r < 0)
                 log_radv_errno(ra, r, "Unable to send Router Advertisement for added route prefix %s, ignoring: %m",
                                strna(addr_p));
@@ -842,7 +858,7 @@ int sd_radv_add_pref64_prefix(sd_radv *ra, sd_radv_pref64_prefix *p) {
                 return 0;
 
         /* If RAs have already been sent, send an RA immediately to announce the newly-added route prefix */
-        r = radv_send(ra, NULL, ra->lifetime_usec);
+        r = radv_send_router(ra, NULL, ra->lifetime_usec);
         if (r < 0)
                 log_radv_errno(ra, r, "Unable to send Router Advertisement for added PREF64 prefix %s, ignoring: %m",
                                strna(addr_p));

src/libsystemd-network/test-ndisc-ra.c

@@ -20,37 +20,6 @@ static struct ether_addr mac_addr = {
         .ether_addr_octet = { 0x78, 0x2b, 0xcb, 0xb3, 0x6d, 0x53 }
 };
 
-static uint8_t advertisement[] = {
-        /* ICMPv6 Router Advertisement, no checksum */
-        0x86, 0x00, 0x00, 0x00,  0x40, 0xc0, 0x00, 0xb4,
-        0x00, 0x00, 0x00, 0x00,  0x00, 0x00, 0x00, 0x00,
-        /* Source Link Layer Address Option */
-        0x01, 0x01, 0x78, 0x2b,  0xcb, 0xb3, 0x6d, 0x53,
-        /* Prefix Information Option */
-        0x03, 0x04, 0x40, 0xc0,  0x00, 0x00, 0x01, 0xf4,
-        0x00, 0x00, 0x01, 0xb8,  0x00, 0x00, 0x00, 0x00,
-        0x20, 0x01, 0x0d, 0xb8,  0xde, 0xad, 0xbe, 0xef,
-        0x00, 0x00, 0x00, 0x00,  0x00, 0x00, 0x00, 0x00,
-        /* Prefix Information Option */
-        0x03, 0x04, 0x40, 0xc0,  0x00, 0x00, 0x0e, 0x10,
-        0x00, 0x00, 0x07, 0x08,  0x00, 0x00, 0x00, 0x00,
-        0x20, 0x01, 0x0d, 0xb8,  0x0b, 0x16, 0xd0, 0x0d,
-        0x00, 0x00, 0x00, 0x00,  0x00, 0x00, 0x00, 0x00,
-        /* Prefix Information Option */
-        0x03, 0x04, 0x30, 0xc0,  0x00, 0x00, 0x0e, 0x10,
-        0x00, 0x00, 0x07, 0x08,  0x00, 0x00, 0x00, 0x00,
-        0x20, 0x01, 0x0d, 0xb8,  0xc0, 0x01, 0x0d, 0xad,
-        0x00, 0x00, 0x00, 0x00,  0x00, 0x00, 0x00, 0x00,
-        /* Recursive DNS Server Option */
-        0x19, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3c,
-        0x20, 0x01, 0x0d, 0xb8, 0xde, 0xad, 0xbe, 0xef,
-        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
-        /* DNS Search List Option */
-        0x1f, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3c,
-        0x03, 0x6c, 0x61, 0x62, 0x05, 0x69, 0x6e, 0x74,
-        0x72, 0x61, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-};
-
 static bool test_stopped;
 static struct {
         struct in6_addr address;
@@ -271,49 +240,91 @@ TEST(radv) {
         assert_se(!ra);
 }
 
-static int radv_recv(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
-        sd_radv *ra = userdata;
-        unsigned char buf[168];
-        size_t i;
+static void dump_message(const uint8_t *buf, size_t len) {
+        assert(len >= sizeof(struct nd_router_advert));
 
-        assert_se(read(test_fd[0], &buf, sizeof(buf)) == sizeof(buf));
+        printf("Received Router Advertisement with lifetime %i sec\n",
+               (buf[6] << 8) + buf[7]);
 
-        /* router lifetime must be zero when test is stopped */
-        if (test_stopped) {
-                advertisement[6] = 0x00;
-                advertisement[7] = 0x00;
-        }
-
-        printf ("Received Router Advertisement with lifetime %i\n",
-                (advertisement[6] << 8) + advertisement[7]);
-
-        /* test only up to buf size, rest is not yet implemented */
-        for (i = 0; i < sizeof(buf); i++) {
+        for (size_t i = 0; i < len; i++) {
                 if (!(i % 8))
                         printf("%3zu: ", i);
 
                 printf("0x%02x", buf[i]);
 
-                assert_se(buf[i] == advertisement[i]);
-
                 if ((i + 1) % 8)
                         printf(", ");
                 else
                         printf("\n");
         }
+}
+
+static void verify_message(const uint8_t *buf, size_t len) {
+        static const uint8_t advertisement[] = {
+                /* ICMPv6 Router Advertisement, no checksum */
+                0x86, 0x00, 0x00, 0x00, 0x40, 0xc0, 0x00, 0xb4,
+                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                /* Source Link Layer Address Option */
+                0x01, 0x01, 0x78, 0x2b, 0xcb, 0xb3, 0x6d, 0x53,
+                /* Prefix Information Option */
+                0x03, 0x04, 0x40, 0xc0, 0x00, 0x00, 0x01, 0xf4,
+                0x00, 0x00, 0x01, 0xb8, 0x00, 0x00, 0x00, 0x00,
+                0x20, 0x01, 0x0d, 0xb8, 0xde, 0xad, 0xbe, 0xef,
+                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                /* Prefix Information Option */
+                0x03, 0x04, 0x40, 0xc0, 0x00, 0x00, 0x0e, 0x10,
+                0x00, 0x00, 0x07, 0x08, 0x00, 0x00, 0x00, 0x00,
+                0x20, 0x01, 0x0d, 0xb8, 0x0b, 0x16, 0xd0, 0x0d,
+                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                /* Prefix Information Option */
+                0x03, 0x04, 0x30, 0xc0, 0x00, 0x00, 0x0e, 0x10,
+                0x00, 0x00, 0x07, 0x08, 0x00, 0x00, 0x00, 0x00,
+                0x20, 0x01, 0x0d, 0xb8, 0xc0, 0x01, 0x0d, 0xad,
+                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                /* Recursive DNS Server Option */
+                0x19, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3c,
+                0x20, 0x01, 0x0d, 0xb8, 0xde, 0xad, 0xbe, 0xef,
+                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
+                /* DNS Search List Option */
+                0x1f, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3c,
+                0x03, 0x6c, 0x61, 0x62, 0x05, 0x69, 0x6e, 0x74,
+                0x72, 0x61, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        };
+
+        /* verify only up to known options, rest is not yet implemented */
+        for (size_t i = 0, m = MIN(len, sizeof(advertisement)); i < m; i++) {
+                if (test_stopped)
+                        switch (i) {
+                        case 6 ... 7: /* router lifetime must be zero on stop. */
+                                assert_se(buf[i] == 0);
+                                continue;
+                        }
+
+                assert_se(buf[i] == advertisement[i]);
+        }
+}
+
+static int radv_recv(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
+        sd_radv *ra = ASSERT_PTR(userdata);
+        _cleanup_free_ uint8_t *buf = NULL;
+        ssize_t buflen;
+
+        buflen = next_datagram_size_fd(fd);
+        assert_se(buflen >= 0);
+        assert_se(buf = new0(uint8_t, buflen));
+
+        assert_se(read(fd, buf, buflen) == buflen);
+
+        dump_message(buf, buflen);
+        verify_message(buf, buflen);
 
         if (test_stopped) {
-                sd_event *e;
-
-                e = sd_radv_get_event(ra);
-                sd_event_exit(e, 0);
-
+                assert_se(sd_event_exit(sd_radv_get_event(ra), 0) >= 0);
                 return 0;
         }
 
         assert_se(sd_radv_stop(ra) >= 0);
         test_stopped = true;
-
         return 0;
 }