src/liboping.c: Provide the TTL on received packets.

Thanks to Vladimir V. Melnikov for the suggestion and initial patch.

diff --git a/src/liboping.c b/src/liboping.c
index bea0be8..0f4c595 100644 (file)
--- a/src/liboping.c
+++ b/src/liboping.c
@@ -112,6 +112,7 @@ struct pinghost
        struct timeval          *timer;
        double                   latency;
        uint32_t                 dropped;
+       int                      recv_ttl;
        char                    *data;
 
        void                    *context;
@@ -422,21 +423,40 @@ static pinghost_t *ping_receive_ipv6 (pinghost_t *ph, char *buffer, size_t buffe
 
 static int ping_receive_one (int fd, pinghost_t *ph, struct timeval *now)
 {
-       char   buffer[4096];
-       ssize_t buffer_len;
-
        struct timeval diff;
-
        pinghost_t *host = NULL;
-
-       struct sockaddr_storage sa;
-       socklen_t               sa_len;
-
-       sa_len = sizeof (sa);
-
-       buffer_len = recvfrom (fd, buffer, sizeof (buffer), 0,
-                       (struct sockaddr *) &sa, &sa_len);
-       if (buffer_len < 0)
+       int family;
+       int recv_ttl;
+       
+       /*
+        * Set up the receive buffer..
+        */
+       struct msghdr msghdr;
+       struct cmsghdr *cmsg;
+       char payload_buffer[4096];
+       ssize_t payload_buffer_len;
+       char control_buffer[4096];
+       struct iovec payload_iovec;
+
+       memset (&payload_iovec, 0, sizeof (payload_iovec));
+       payload_iovec.iov_base = payload_buffer;
+       payload_iovec.iov_len = sizeof (payload_buffer);
+
+       memset (&msghdr, 0, sizeof (msghdr));
+       /* unspecified source address */
+       msghdr.msg_name = NULL;
+       msghdr.msg_namelen = 0;
+       /* output buffer vector, see readv(2) */
+       msghdr.msg_iov = &payload_iovec;
+       msghdr.msg_iovlen = 1;
+       /* output buffer for control messages */
+       msghdr.msg_control = control_buffer;
+       msghdr.msg_controllen = sizeof (control_buffer);
+       /* flags; this is an output only field.. */
+       msghdr.msg_flags = 0;
+
+       payload_buffer_len = recvmsg (fd, &msghdr, /* flags = */ 0);
+       if (payload_buffer_len < 0)
        {
 #if WITH_DEBUG
                char errbuf[PING_ERRMSG_LEN];
@@ -445,19 +465,71 @@ static int ping_receive_one (int fd, pinghost_t *ph, struct timeval *now)
 #endif
                return (-1);
        }
+       dprintf ("Read %zi bytes from fd = %i\n", payload_buffer_len, fd);
+
+       /* Iterate over all auxiliary data in msghdr */
+       family = -1;
+       recv_ttl = -1;
+       for (cmsg = CMSG_FIRSTHDR (&msghdr); /* {{{ */
+                       cmsg != NULL;
+                       cmsg = CMSG_NXTHDR (&msghdr, cmsg))
+       {
+               if (cmsg->cmsg_level == IPPROTO_IP) /* {{{ */
+               {
+                       family = AF_INET;
+                       if (cmsg->cmsg_type == IP_TTL)
+                       {
+                               memcpy (&recv_ttl, CMSG_DATA (cmsg),
+                                               sizeof (recv_ttl));
+                               dprintf ("TTLv4 = %i;\n", recv_ttl);
+                       }
+                       else
+                       {
+                               dprintf ("Not handling option %i.\n",
+                                               cmsg->cmsg_type);
+                       }
+               } /* }}} */
+               else if (cmsg->cmsg_level == IPPROTO_IPV6) /* {{{ */
+               {
+                       family = AF_INET6;
+                       if (cmsg->cmsg_type == IPV6_HOPLIMIT)
+                       {
+                               memcpy (&recv_ttl, CMSG_DATA (cmsg),
+                                               sizeof (recv_ttl));
+                               dprintf ("TTLv6 = %i;\n", recv_ttl);
+                       }
+                       else
+                       {
+                               dprintf ("Not handling option %i.\n",
+                                               cmsg->cmsg_type);
+                       }
+               } /* }}} */
+               else
+               {
+                       dprintf ("Don't know how to handle "
+                                       "unknown protocol %i.\n",
+                                       cmsg->cmsg_level);
+               }
+       } /* }}} for (cmsg) */
 
-       dprintf ("Read %zi bytes from fd = %i\n", buffer_len, fd);
-
-       if (sa.ss_family == AF_INET)
+       if (family == AF_INET)
        {
-               if ((host = ping_receive_ipv4 (ph, buffer, buffer_len)) == NULL)
+               host = ping_receive_ipv4 (ph, payload_buffer, payload_buffer_len);
+               if (host == NULL)
                        return (-1);
        }
-       else if (sa.ss_family == AF_INET6)
+       else if (family == AF_INET6)
        {
-               if ((host = ping_receive_ipv6 (ph, buffer, buffer_len)) == NULL)
+               host = ping_receive_ipv6 (ph, payload_buffer, payload_buffer_len);
+               if (host == NULL)
                        return (-1);
        }
+       else
+       {
+               dprintf ("ping_receive_one: Unknown address family %i.\n",
+                               family);
+               return (-1);
+       }
 
        dprintf ("rcvd: %12i.%06i\n",
                        (int) now->tv_sec,
@@ -479,6 +551,8 @@ static int ping_receive_one (int fd, pinghost_t *ph, struct timeval *now)
        host->latency  = ((double) diff.tv_usec) / 1000.0;
        host->latency += ((double) diff.tv_sec)  * 1000.0;
 
+       host->recv_ttl = recv_ttl;
+
        timerclear (host->timer);
 
        return (0);
@@ -1246,6 +1320,21 @@ int ping_host_add (pingobj_t *obj, const char *host)
                }
 #endif /* AI_CANONNAME */
 
+               if (ph->addrfamily == AF_INET)
+               {
+                       int opt = 1;
+
+                       setsockopt (ph->fd, IPPROTO_IP, IP_RECVTTL,
+                                       &opt, sizeof (opt));
+               }
+               else if (ph->addrfamily == AF_INET6)
+               {
+                       int opt = 1;
+
+                       setsockopt (ph->fd, IPPROTO_IPV6, IPV6_RECVHOPLIMIT,
+                                       &opt, sizeof (opt));
+               }
+
                break;
        }
 
@@ -1281,7 +1370,7 @@ int ping_host_add (pingobj_t *obj, const char *host)
        ping_set_ttl (ph, obj->ttl);
 
        return (0);
-}
+} /* int ping_host_add */
 
 int ping_host_remove (pingobj_t *obj, const char *host)
 {
@@ -1435,6 +1524,15 @@ int ping_iterator_get_info (pingobj_iter_t *iter, int info,
                        strncpy ((char *) buffer, iter->data, orig_buffer_len);
                        ret = 0;
                        break;
+
+               case PING_INFO_RECV_TTL:
+                       ret = ENOMEM;
+                       *buffer_len = sizeof (int);
+                       if (orig_buffer_len < sizeof (int))
+                               break;
+                       *((int *) buffer) = iter->recv_ttl;
+                       ret = 0;
+                       break;
        }
 
        return (ret);

diff --git a/src/mans/ping_iterator_get_info.pod b/src/mans/ping_iterator_get_info.pod
index e3b2006..1d4e8cf 100644 (file)
--- a/src/mans/ping_iterator_get_info.pod
+++ b/src/mans/ping_iterator_get_info.pod
@@ -73,8 +73,15 @@ echo responses being received or not. The buffer should hold an integer.
 =item B<PING_INFO_IDENT>
 
 Return the ident that is put into every ICMP packet sent to this host. Per
-convention this usually is the PID of the sending process, but since liboping
-can handle several hosts in parallel it uses a (pseudo-)random number here. The
+convention this usually is the PID of the sending process, but since
+I<liboping> can handle several hosts in parallel it uses a (pseudo-)random
+number here. The buffer should be big enough to hold an integer value.
+
+=item B<PING_INFO_RECV_TTL>
+
+Returns the I<time to live> (TTL) of the received network packets. This number
+depends on the value that was used by the remote host when it sent the echo
+reply and has nothing to do with the B<PING_OPT_TTL> of L<ping_setopt(3)>. The
 buffer should be big enough to hold an integer value.
 
 =back

diff --git a/src/oping.h b/src/oping.h
index 10a106a..fe80ff5 100644 (file)
--- a/src/oping.h
+++ b/src/oping.h
@@ -81,15 +81,16 @@ int ping_host_remove (pingobj_t *obj, const char *host);
 pingobj_iter_t *ping_iterator_get (pingobj_t *obj);
 pingobj_iter_t *ping_iterator_next (pingobj_iter_t *iter);
 
-#define PING_INFO_HOSTNAME 1
-#define PING_INFO_ADDRESS  2
-#define PING_INFO_FAMILY   3
-#define PING_INFO_LATENCY  4
-#define PING_INFO_SEQUENCE 5
-#define PING_INFO_IDENT    6
-#define PING_INFO_DATA     7
-#define PING_INFO_USERNAME 8
-#define PING_INFO_DROPPED  9
+#define PING_INFO_HOSTNAME  1
+#define PING_INFO_ADDRESS   2
+#define PING_INFO_FAMILY    3
+#define PING_INFO_LATENCY   4
+#define PING_INFO_SEQUENCE  5
+#define PING_INFO_IDENT     6
+#define PING_INFO_DATA      7
+#define PING_INFO_USERNAME  8
+#define PING_INFO_DROPPED   9
+#define PING_INFO_RECV_TTL 10
 int ping_iterator_get_info (pingobj_iter_t *iter, int info,
                void *buffer, size_t *buffer_len);