Added netlink error message support to be able to provide return values.

Renamed some structure elements. Updated usage text.

diff --git a/cangw.c b/cangw.c
index d6dff901cb53858a62b8c277700502aec84ce4f0..0d33333f14c8715b50cbe0c061197ca8d9e05168 100644 (file)
--- a/cangw.c
+++ b/cangw.c
@@ -99,7 +99,7 @@ void print_usage(char *prg)
 {
        fprintf(stderr, "\nUsage: %s [options]\n\n", prg);
        fprintf(stderr, "Commands:  -A (add a new rule)\n");
-       fprintf(stderr, "           -D (delete a rule)             [not yet implemented]\n");
+       fprintf(stderr, "           -D (delete a rule)\n");
        fprintf(stderr, "           -F (flush - delete all rules)  [not yet implemented]\n");
        fprintf(stderr, "           -L (list all rules)            [not yet implemented]\n");
        fprintf(stderr, "Mandatory: -s <src_dev>  (source netdevice)\n");
@@ -209,12 +209,16 @@ int main(int argc, char **argv)
        int have_filter = 0;
 
        struct {
-               struct nlmsghdr n;
-               struct rtcanmsg r;
+               struct nlmsghdr nh;
+               struct rtcanmsg rtcan;
                char buf[200];
 
        } req;
 
+       char rxbuf[8192]; /* netlink receive buffer */
+       struct nlmsghdr *nlh;
+       struct nlmsgerr *rte;
+
        struct can_filter filter;
        struct sockaddr_nl nladdr;
 
@@ -248,19 +252,19 @@ int main(int argc, char **argv)
                        break;
 
                case 's':
-                       req.r.src_ifindex = if_nametoindex(optarg);
+                       req.rtcan.src_ifindex = if_nametoindex(optarg);
                        break;
 
                case 'd':
-                       req.r.dst_ifindex = if_nametoindex(optarg);
+                       req.rtcan.dst_ifindex = if_nametoindex(optarg);
                        break;
 
                case 't':
-                       req.r.can_txflags |= CAN_GW_TXFLAGS_SRC_TSTAMP;
+                       req.rtcan.can_txflags |= CAN_GW_TXFLAGS_SRC_TSTAMP;
                        break;
 
                case 'e':
-                       req.r.can_txflags |= CAN_GW_TXFLAGS_ECHO;
+                       req.rtcan.can_txflags |= CAN_GW_TXFLAGS_ECHO;
                        break;
 
                case 'f':
@@ -296,7 +300,7 @@ int main(int argc, char **argv)
        }
 
        if ((argc - optind != 0) || (cmd == UNSPEC) ||
-           (!req.r.src_ifindex) || (!req.r.dst_ifindex)) {
+           (!req.rtcan.src_ifindex) || (!req.rtcan.dst_ifindex)) {
                print_usage(basename(argv[0]));
                exit(1);
        }
@@ -306,13 +310,13 @@ int main(int argc, char **argv)
        switch (cmd) {
 
        case ADD:
-               req.n.nlmsg_flags = NLM_F_REQUEST;
-               req.n.nlmsg_type  = RTM_NEWROUTE;
+               req.nh.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
+               req.nh.nlmsg_type  = RTM_NEWROUTE;
                break;
 
        case DEL:
-               req.n.nlmsg_flags = NLM_F_REQUEST;
-               req.n.nlmsg_type  = RTM_DELROUTE;
+               req.nh.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
+               req.nh.nlmsg_type  = RTM_DELROUTE;
                break;
 
        default:
@@ -321,15 +325,15 @@ int main(int argc, char **argv)
                break;
        }
 
-       req.n.nlmsg_len   = NLMSG_LENGTH(sizeof(struct rtcanmsg));
-       req.n.nlmsg_seq   = 0;
+       req.nh.nlmsg_len   = NLMSG_LENGTH(sizeof(struct rtcanmsg));
+       req.nh.nlmsg_seq   = 0;
 
-       req.r.can_family  = AF_CAN;
+       req.rtcan.can_family  = AF_CAN;
 
        /* add new attributes here */
 
        if (have_filter)
-               addattr_l(&req.n, sizeof(req), CGW_FILTER, &filter, sizeof(filter));
+               addattr_l(&req.nh, sizeof(req), CGW_FILTER, &filter, sizeof(filter));
 
        // a better example code
        // modmsg.modtype = CGW_MOD_ID;
@@ -337,18 +341,40 @@ int main(int argc, char **argv)
 
        /* add up to CGW_MOD_FUNCS modification definitions */
        for (i = 0; i < modidx; i++)
-               addattr_l(&req.n, sizeof(req), modmsg[i].instruction, &modmsg[i], CGW_MODATTR_LEN);
+               addattr_l(&req.nh, sizeof(req), modmsg[i].instruction, &modmsg[i], CGW_MODATTR_LEN);
 
        memset(&nladdr, 0, sizeof(nladdr));
        nladdr.nl_family = AF_NETLINK;
        nladdr.nl_pid    = 0;
        nladdr.nl_groups = 0;
 
-       err = sendto(s, &req, req.n.nlmsg_len, 0,
+       err = sendto(s, &req, req.nh.nlmsg_len, 0,
                     (struct sockaddr*)&nladdr, sizeof(nladdr));
+       if (err < 0) {
+               perror("netlink sendto");
+               return err;
+       }
+
+       // clean netlink receive buffer
+       bzero(rxbuf, sizeof(rxbuf));
+
+       if (cmd == ADD || cmd == DEL) {
 
-       if (err < 0)
-               perror("PF_CAN netlink gateway answered ");
+               err = recv(s, &rxbuf, sizeof(rxbuf), 0);
+               if (err < 0) {
+                       perror("netlink recv");
+                       return err;
+               }
+               nlh = (struct nlmsghdr *)rxbuf;
+               if (nlh->nlmsg_type != NLMSG_ERROR) {
+                       fprintf(stderr, "unexpected netlink answer of type %d\n", nlh->nlmsg_type);
+                       return -EINVAL;
+               }
+               rte = (struct nlmsgerr *)NLMSG_DATA(nlh);
+               err = rte->error;
+               if (err < 0)
+                       fprintf(stderr, "netlink error %d (%s)\n", err, strerror(abs(err)));
+       }
 
        close(s);