sd-radv: Receive Router Solicitations

Receive Router Solicitations and send a unicast Router Advertisment
in response. Refactor ICMPv6 packet handling code so that the common
ICMPv6 validation parts are reused between the existing router
discovery and the new functionality adding reception of Router
Solicitation messages.

1 files changed, 72 insertions, 2 deletions

diff --git a/src/libsystemd-network/sd-radv.c b/src/libsystemd-network/sd-radv.c
index 1b60af0dd7..f23275a80c 100644
--- a/src/libsystemd-network/sd-radv.c
+++ b/src/libsystemd-network/sd-radv.c
@@ -93,6 +93,9 @@ static void radv_reset(sd_radv *ra) {
         ra->timeout_event_source =
                 sd_event_source_unref(ra->timeout_event_source);
 
+        ra->recv_event_source =
+                sd_event_source_unref(ra->recv_event_source);
+
         ra->ra_sent = 0;
 }
 
@@ -160,8 +163,9 @@ static int radv_send(sd_radv *ra, const struct in6_addr *dst,
                 .msg_iov = iov,
         };
 
-        if (dst)
+        if (dst && !in_addr_is_null(AF_INET6, (union in_addr_union*) dst))
                 dst_addr.sin6_addr = *dst;
+
         adv.nd_ra_type = ND_ROUTER_ADVERT;
         adv.nd_ra_curhoplimit = ra->hop_limit;
         adv.nd_ra_flags_reserved = ra->flags;
@@ -198,6 +202,63 @@ static int radv_send(sd_radv *ra, const struct in6_addr *dst,
         return 0;
 }
 
+static int radv_recv(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
+        sd_radv *ra = userdata;
+        _cleanup_free_ char *addr = NULL;
+        struct in6_addr src;
+        triple_timestamp timestamp;
+        int r;
+        ssize_t buflen;
+        _cleanup_free_ char *buf = NULL;
+
+        assert(s);
+        assert(ra);
+        assert(ra->event);
+
+        buflen = next_datagram_size_fd(fd);
+
+        if ((unsigned) buflen < sizeof(struct nd_router_solicit))
+                return log_radv("Too short packet received");
+
+        buf = new0(char, buflen);
+        if (!buf)
+                return 0;
+
+        r = icmp6_receive(fd, buf, buflen, &src, &timestamp);
+        if (r < 0) {
+                switch (r) {
+                case -EADDRNOTAVAIL:
+                        (void) in_addr_to_string(AF_INET6, (union in_addr_union*) &src, &addr);
+                        log_radv("Received RS from non-link-local address %s. Ignoring", addr);
+                        break;
+
+                case -EMULTIHOP:
+                        log_radv("Received RS with invalid hop limit. Ignoring.");
+                        break;
+
+                case -EPFNOSUPPORT:
+                        log_radv("Received invalid source address from ICMPv6 socket. Ignoring.");
+                        break;
+
+                default:
+                        log_radv_warning_errno(r, "Error receiving from ICMPv6 socket: %m");
+                        break;
+                }
+
+                return 0;
+        }
+
+        (void) in_addr_to_string(AF_INET6, (union in_addr_union*) &src, &addr);
+
+        r = radv_send(ra, &src, ra->lifetime);
+        if (r < 0)
+                log_radv_warning_errno(r, "Unable to send solicited Router Advertisment to %s: %m", addr);
+        else
+                log_radv("Sent solicited Router Advertisement to %s", addr);
+
+        return 0;
+}
+
 static usec_t radv_compute_timeout(usec_t min, usec_t max) {
         assert_return(min <= max, SD_RADV_DEFAULT_MIN_TIMEOUT_USEC);
 
@@ -313,7 +374,16 @@ _public_ int sd_radv_start(sd_radv *ra) {
                 goto fail;
 
         ra->fd = r;
-        r = 0;
+
+        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 = SD_RADV_STATE_ADVERTISING;