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, 0 deletions

diff --git a/src/libsystemd-network/icmp6-util.c b/src/libsystemd-network/icmp6-util.c
index f1cb0bc8a0..7fbebd6f27 100644
--- a/src/libsystemd-network/icmp6-util.c
+++ b/src/libsystemd-network/icmp6-util.c
@@ -32,6 +32,7 @@
 #include "fd-util.h"
 #include "icmp6-util.h"
 #include "socket-util.h"
+#include "in-addr-util.h"
 
 #define IN6ADDR_ALL_ROUTERS_MULTICAST_INIT \
         { { { 0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, \
@@ -164,3 +165,74 @@ int icmp6_send_router_solicitation(int s, const struct ether_addr *ether_addr) {
 
         return 0;
 }
+
+int icmp6_receive(int fd, void *buffer, size_t size, struct in6_addr *dst,
+                  triple_timestamp *timestamp) {
+        union {
+                struct cmsghdr cmsghdr;
+                uint8_t buf[CMSG_SPACE(sizeof(int)) + /* ttl */
+                            CMSG_SPACE(sizeof(struct timeval))];
+        } control = {};
+        struct iovec iov = {};
+        union sockaddr_union sa = {};
+        struct msghdr msg = {
+                .msg_name = &sa.sa,
+                .msg_namelen = sizeof(sa),
+                .msg_iov = &iov,
+                .msg_iovlen = 1,
+                .msg_control = &control,
+                .msg_controllen = sizeof(control),
+        };
+        struct cmsghdr *cmsg;
+        ssize_t len;
+
+        iov.iov_base = buffer;
+        iov.iov_len = size;
+
+        len = recvmsg(fd, &msg, MSG_DONTWAIT);
+        if (len < 0) {
+                if (errno == EAGAIN || errno == EINTR)
+                        return 0;
+
+                return -errno;
+        }
+
+        if ((size_t) len != size)
+                return -EINVAL;
+
+        if (msg.msg_namelen == sizeof(struct sockaddr_in6) &&
+            sa.in6.sin6_family == AF_INET6)  {
+
+                *dst = sa.in6.sin6_addr;
+                if (in_addr_is_link_local(AF_INET6, (union in_addr_union*) dst) <= 0)
+                        return -EADDRNOTAVAIL;
+
+        } else if (msg.msg_namelen > 0)
+                return -EPFNOSUPPORT;
+
+        /* namelen == 0 only happens when running the test-suite over a socketpair */
+
+        assert(!(msg.msg_flags & MSG_CTRUNC));
+        assert(!(msg.msg_flags & MSG_TRUNC));
+
+        CMSG_FOREACH(cmsg, &msg) {
+                if (cmsg->cmsg_level == SOL_IPV6 &&
+                    cmsg->cmsg_type == IPV6_HOPLIMIT &&
+                    cmsg->cmsg_len == CMSG_LEN(sizeof(int))) {
+                        int hops = *(int*) CMSG_DATA(cmsg);
+
+                        if (hops != 255)
+                                return -EMULTIHOP;
+                }
+
+                if (cmsg->cmsg_level == SOL_SOCKET &&
+                    cmsg->cmsg_type == SO_TIMESTAMP &&
+                    cmsg->cmsg_len == CMSG_LEN(sizeof(struct timeval)))
+                        triple_timestamp_from_realtime(timestamp, timeval_load((struct timeval*) CMSG_DATA(cmsg)));
+        }
+
+        if (!triple_timestamp_is_set(timestamp))
+                triple_timestamp_get(timestamp);
+
+        return 0;
+}