actions: add skbmod action

This action is intended to be an upgrade from a usability perspective
from pedit (as well as operational debugability).
Compare this:

sudo tc filter add dev $ETH parent 1: protocol ip prio 10 \
u32 match ip protocol 1 0xff flowid 1:2 \
action pedit munge offset -14 u8 set 0x02 \
    munge offset -13 u8 set 0x15 \
    munge offset -12 u8 set 0x15 \
    munge offset -11 u8 set 0x15 \
    munge offset -10 u16 set 0x1515 \
    pipe

to:

sudo tc filter add dev $ETH parent 1: protocol ip prio 10 \
u32 match ip protocol 1 0xff flowid 1:2 \
action skbmod dmac 02:15:15:15:15:15

Or worse, try to debug a policy with destination mac, source mac and
etherype. Then make that a hundred rules and you'll get my point.

The most important ethernet use case at the moment is when redirecting or
mirroring packets to a remote machine. The dst mac address needs a re-write
so that it doesn't get dropped or confuse an interconnecting (learning) switch
or dropped by a target machine (which looks at the dst mac).

In the future common use cases on pedit can be migrated to this action
(as an example different fields in ip v4/6, transports like tcp/udp/sctp
etc). For this first cut, this allows modifying basic ethernet header.

Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>

diff --git a/tc/m_skbmod.c b/tc/m_skbmod.c
new file mode 100644 (file)
index 0000000..b7f4765
--- /dev/null
+++ b/tc/m_skbmod.c
@@ -0,0 +1,260 @@
+/*
+ * m_skbmod.c  skb modifier action module
+ *
+ *             This program is free software; you can distribute it and/or
+ *             modify it under the terms of the GNU General Public License
+ *             as published by the Free Software Foundation; either version
+ *             2 of the License, or (at your option) any later version.
+ *
+ * Authors:  J Hadi Salim (jhs@mojatatu.com)
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <syslog.h>
+#include <fcntl.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <string.h>
+#include <linux/netdevice.h>
+
+#include "rt_names.h"
+#include "utils.h"
+#include "tc_util.h"
+#include <linux/tc_act/tc_skbmod.h>
+
+static void skbmod_explain(void)
+{
+       fprintf(stderr,
+               "Usage:... skbmod {[set <SETTABLE>] [swap <SWAPABLE>]} [CONTROL] [index INDEX]\n");
+       fprintf(stderr, "where SETTABLE is: [dmac DMAC] [smac SMAC] [etype ETYPE] \n");
+       fprintf(stderr, "where SWAPABLE is: \"mac\" to swap mac addresses\n");
+       fprintf(stderr, "note: \"swap mac\" is done after any outstanding D/SMAC change\n");
+       fprintf(stderr,
+               "\tDMAC := 6 byte Destination MAC address\n"
+               "\tSMAC := optional 6 byte Source MAC address\n"
+               "\tETYPE := optional 16 bit ethertype\n"
+               "\tCONTROL := reclassify|pipe|drop|continue|ok\n"
+               "\tINDEX := skbmod index value to use\n");
+}
+
+static void skbmod_usage(void)
+{
+       skbmod_explain();
+       exit(-1);
+}
+
+static int parse_skbmod(struct action_util *a, int *argc_p, char ***argv_p,
+                       int tca_id, struct nlmsghdr *n)
+{
+       int argc = *argc_p;
+       char **argv = *argv_p;
+       int ok = 0;
+       struct tc_skbmod p;
+       struct rtattr *tail;
+       char dbuf[ETH_ALEN];
+       char sbuf[ETH_ALEN];
+       __u16 skbmod_etype = 0;
+       char *daddr = NULL;
+       char *saddr = NULL;
+
+       memset(&p, 0, sizeof(p));
+       p.action = TC_ACT_PIPE; /* good default */
+
+       if (argc <= 0)
+               return -1;
+
+       while (argc > 0) {
+               if (matches(*argv, "skbmod") == 0) {
+                       NEXT_ARG();
+                       continue;
+               } else if (matches(*argv, "swap") == 0) {
+                       NEXT_ARG();
+                       continue;
+               } else if (matches(*argv, "mac") == 0) {
+                       p.flags |= SKBMOD_F_SWAPMAC;
+                       ok += 1;
+               } else if (matches(*argv, "set") == 0) {
+                       NEXT_ARG();
+                       continue;
+               } else if (matches(*argv, "etype") == 0) {
+                       NEXT_ARG();
+                       if (get_u16(&skbmod_etype, *argv, 0))
+                               invarg("ethertype is invalid", *argv);
+                       fprintf(stderr, "skbmod etype 0x%x\n", skbmod_etype);
+                       p.flags |= SKBMOD_F_ETYPE;
+                       ok += 1;
+               } else if (matches(*argv, "dmac") == 0) {
+                       NEXT_ARG();
+                       daddr = *argv;
+                       if (sscanf(daddr, "%hhx:%hhx:%hhx:%hhx:%hhx:%hhx",
+                                  dbuf, dbuf + 1, dbuf + 2,
+                                  dbuf + 3, dbuf + 4, dbuf + 5) != 6) {
+                               fprintf(stderr, "Invalid dst mac address %s\n",
+                                       daddr);
+                               return -1;
+                       }
+                       p.flags |= SKBMOD_F_DMAC;
+                       fprintf(stderr, "dst MAC address <%s>\n", daddr);
+                       ok += 1;
+
+               } else if (matches(*argv, "smac") == 0) {
+                       NEXT_ARG();
+                       saddr = *argv;
+                       if (sscanf(saddr, "%hhx:%hhx:%hhx:%hhx:%hhx:%hhx",
+                                  sbuf, sbuf + 1, sbuf + 2,
+                                  sbuf + 3, sbuf + 4, sbuf + 5) != 6) {
+                               fprintf(stderr, "Invalid smac address %s\n",
+                                       saddr);
+                               return -1;
+                       }
+                       p.flags |= SKBMOD_F_SMAC;
+                       fprintf(stderr, "src MAC address <%s>\n", saddr);
+                       ok += 1;
+               } else if (matches(*argv, "help") == 0) {
+                       skbmod_usage();
+               } else {
+                       break;
+               }
+
+               argc--;
+               argv++;
+       }
+
+       if (argc) {
+               if (matches(*argv, "reclassify") == 0) {
+                       p.action = TC_ACT_RECLASSIFY;
+                       argc--;
+                       argv++;
+               } else if (matches(*argv, "pipe") == 0) {
+                       p.action = TC_ACT_PIPE;
+                       argc--;
+                       argv++;
+               } else if (matches(*argv, "drop") == 0 ||
+                          matches(*argv, "shot") == 0) {
+                       p.action = TC_ACT_SHOT;
+                       argc--;
+                       argv++;
+               } else if (matches(*argv, "continue") == 0) {
+                       p.action = TC_ACT_UNSPEC;
+                       argc--;
+                       argv++;
+               } else if (matches(*argv, "pass") == 0 ||
+                          matches(*argv, "ok") == 0) {
+                       p.action = TC_ACT_OK;
+                       argc--;
+                       argv++;
+               }
+       }
+
+       if (argc) {
+               if (matches(*argv, "index") == 0) {
+                       NEXT_ARG();
+                       if (get_u32(&p.index, *argv, 0)) {
+                               fprintf(stderr, "skbmod: Illegal \"index\"\n");
+                               return -1;
+                       }
+                       ok++;
+                       argc--;
+                       argv++;
+               }
+       }
+
+       if (!ok) {
+               fprintf(stderr, "skbmod requires at least one option\n");
+               skbmod_usage();
+       }
+
+       tail = NLMSG_TAIL(n);
+       addattr_l(n, MAX_MSG, tca_id, NULL, 0);
+       addattr_l(n, MAX_MSG, TCA_SKBMOD_PARMS, &p, sizeof(p));
+
+       if (daddr)
+               addattr_l(n, MAX_MSG, TCA_SKBMOD_DMAC, dbuf, ETH_ALEN);
+       if (skbmod_etype)
+               addattr16(n, MAX_MSG, TCA_SKBMOD_ETYPE, skbmod_etype);
+       if (saddr)
+               addattr_l(n, MAX_MSG, TCA_SKBMOD_SMAC, sbuf, ETH_ALEN);
+
+       tail->rta_len = (void *)NLMSG_TAIL(n) - (void *)tail;
+
+       *argc_p = argc;
+       *argv_p = argv;
+       return 0;
+}
+
+static int print_skbmod(struct action_util *au, FILE *f, struct rtattr *arg)
+{
+       struct tc_skbmod *p = NULL;
+       struct rtattr *tb[TCA_SKBMOD_MAX + 1];
+       __u16 skbmod_etype = 0;
+       int has_optional = 0;
+       SPRINT_BUF(b1);
+       SPRINT_BUF(b2);
+
+       if (arg == NULL)
+               return -1;
+
+       parse_rtattr_nested(tb, TCA_SKBMOD_MAX, arg);
+
+       if (tb[TCA_SKBMOD_PARMS] == NULL) {
+               fprintf(f, "[NULL skbmod parameters]");
+               return -1;
+       }
+
+       p = RTA_DATA(tb[TCA_SKBMOD_PARMS]);
+
+       fprintf(f, "skbmod action %s ", action_n2a(p->action));
+
+       if (tb[TCA_SKBMOD_ETYPE]) {
+               skbmod_etype = rta_getattr_u16(tb[TCA_SKBMOD_ETYPE]);
+               has_optional = 1;
+               fprintf(f, "set etype 0x%X ", skbmod_etype);
+       }
+
+       if (has_optional)
+               fprintf(f, "\n\t ");
+
+       if (tb[TCA_SKBMOD_DMAC]) {
+               has_optional = 1;
+               fprintf(f, "set dmac %s ",
+                       ll_addr_n2a(RTA_DATA(tb[TCA_SKBMOD_DMAC]),
+                                   RTA_PAYLOAD(tb[TCA_SKBMOD_DMAC]), 0, b1,
+                                   sizeof(b1)));
+
+       }
+
+       if (tb[TCA_SKBMOD_SMAC]) {
+               has_optional = 1;
+               fprintf(f, "set smac %s ",
+                       ll_addr_n2a(RTA_DATA(tb[TCA_SKBMOD_SMAC]),
+                                   RTA_PAYLOAD(tb[TCA_SKBMOD_SMAC]), 0, b2,
+                                   sizeof(b2)));
+       }
+
+       if (p->flags & SKBMOD_F_SWAPMAC)
+               fprintf(f, "swap mac ");
+
+       fprintf(f, "\n\t index %d ref %d bind %d", p->index, p->refcnt,
+               p->bindcnt);
+       if (show_stats) {
+               if (tb[TCA_SKBMOD_TM]) {
+                       struct tcf_t *tm = RTA_DATA(tb[TCA_SKBMOD_TM]);
+
+                       print_tm(f, tm);
+               }
+       }
+
+       fprintf(f, "\n");
+
+       return 0;
+}
+
+struct action_util skbmod_action_util = {
+       .id = "skbmod",
+       .parse_aopt = parse_skbmod,
+       .print_aopt = print_skbmod,
+};