netdev - Re: [PATCH iproute2] Add "show" subcommand to "ip fou"

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Message-id: <9F9BDF85-1400-4CA0-A852-02EE02E7B64C@apple.com>
Date:   Fri, 03 Nov 2017 10:19:22 -0700
From:   Greg Greenway <ggreenway@...le.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH iproute2] Add "show" subcommand to "ip fou"

On Nov 1, 2017, at 2:03 PM, Stephen Hemminger <stephen@...workplumber.org> wrote:
> 
> On Tue, 31 Oct 2017 13:00:47 -0700
> Greg Greenway <ggreenway@...le.com> wrote:
> 
>> +	if (tb[FOU_ATTR_AF]) {
>> +		family = rta_getattr_u8(tb[FOU_ATTR_AF]);
>> +		if (family == AF_INET)
>> +			family_str = "AF_INET";
>> +		else if (family == AF_INET6)
>> +			family_str = "AF_INET6";
>> +		else
>> +			family_str = "unknown";
>> +		fprintf(fp, "af %s ", family_str);
> 
> The unwritten rule for ip commands is that the show function
> must format the output with same command syntax as the other commands set/add/delete.
> Since there is no "af AF_INET" option to ip fou, this breaks that convention.
> Either ignore the address family, change the add command, or output with same
> syntax (-6); preferably the latter.

That makes sense.  Here's a corrected version.  It also avoids a trailing-space in the output.

From: Greg Greenway <ggreenway@...le.com>
Date: Tue, 31 Oct 2017 12:47:35 -0700
Subject: [PATCH] Add "show" subcommand to "ip fou".

Sample output:

$ sudo ./ip/ip fou add port 111 ipproto 11
$ sudo ./ip/ip fou add port 222 ipproto 22 -6
$ ./ip/ip fou show
port 222 ipproto 22 -6
port 111 ipproto 11

Signed-off-by: Greg Greenway <ggreenway@...le.com>
---
 ip/ipfou.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/ip/ipfou.c b/ip/ipfou.c
index 00dbe15..ecbaf11 100644
--- a/ip/ipfou.c
+++ b/ip/ipfou.c
@@ -28,6 +28,7 @@ static void usage(void)
        fprintf(stderr, "Usage: ip fou add port PORT "
                "{ ipproto PROTO  | gue } [ -6 ]\n");
        fprintf(stderr, "       ip fou del port PORT [ -6 ]\n");
+       fprintf(stderr, "       ip fou show\n");
        fprintf(stderr, "\n");
        fprintf(stderr, "Where: PROTO { ipproto-name | 1..255 }\n");
        fprintf(stderr, "       PORT { 1..65535 }\n");
@@ -134,6 +135,63 @@ static int do_del(int argc, char **argv)
        return 0;
 }
 
+static int print_fou_mapping(const struct sockaddr_nl *who,
+                                struct nlmsghdr *n, void *arg)
+{
+       FILE *fp = (FILE *)arg;
+       struct genlmsghdr *ghdr;
+       struct rtattr *tb[FOU_ATTR_MAX + 1];
+       int len = n->nlmsg_len;
+       unsigned family;
+
+       if (n->nlmsg_type != genl_family)
+               return 0;
+
+       len -= NLMSG_LENGTH(GENL_HDRLEN);
+       if (len < 0)
+               return -1;
+
+       ghdr = NLMSG_DATA(n);
+       parse_rtattr(tb, FOU_ATTR_MAX, (void *) ghdr + GENL_HDRLEN, len);
+
+       if (tb[FOU_ATTR_PORT])
+               fprintf(fp, "port %u", ntohs(rta_getattr_u16(tb[FOU_ATTR_PORT])));
+       if (tb[FOU_ATTR_TYPE] && rta_getattr_u8(tb[FOU_ATTR_TYPE]) == FOU_ENCAP_GUE)
+               fprintf(fp, " gue");
+       else if (tb[FOU_ATTR_IPPROTO])
+               fprintf(fp, " ipproto %u", rta_getattr_u8(tb[FOU_ATTR_IPPROTO]));
+       if (tb[FOU_ATTR_AF]) {
+               family = rta_getattr_u8(tb[FOU_ATTR_AF]);
+               if (family == AF_INET6)
+                       fprintf(fp, " -6");
+       }
+       fprintf(fp, "\n");
+
+       return 0;
+}
+
+static int do_show(int argc, char **argv)
+{
+       FOU_REQUEST(req, 4096, FOU_CMD_GET, NLM_F_REQUEST | NLM_F_DUMP);
+
+       if (argc > 0) {
+               fprintf(stderr, "\"ip fou show\" does not take any arguments.\n");
+               return -1;
+       }
+
+       if (rtnl_send(&genl_rth, &req.n, req.n.nlmsg_len) < 0) {
+               perror("Cannot send show request");
+               exit(1);
+       }
+
+       if (rtnl_dump_filter(&genl_rth, print_fou_mapping, stdout) < 0) {
+               fprintf(stderr, "Dump terminated\n");
+               return 1;
+       }
+
+       return 0;
+}
+
 int do_ipfou(int argc, char **argv)
 {
        if (argc < 1)
@@ -149,6 +207,8 @@ int do_ipfou(int argc, char **argv)
                return do_add(argc-1, argv+1);
        if (matches(*argv, "delete") == 0)
                return do_del(argc-1, argv+1);
+       if (matches(*argv, "show") == 0)
+               return do_show(argc-1, argv+1);
        fprintf(stderr, "Command \"%s\" is unknown, try \"ip fou help\".\n", *argv);
        exit(-1);
 }
-- 
2.7.4