The new action inheritdsfield copies the field DS of
IPv4 and IPv6 packets into skb->priority. This enables
later classification of packets based on the DS field.

v2:
* Align the output syntax with the input syntax

* Fix the style issues

Original idea by Jamal Hadi Salim <j...@mojatatu.com>

Signed-off-by: Qiaobin Fu <qiaob...@bu.edu>
Reviewed-by: Michel Machado <mic...@digirati.com.br>
Reviewed-by: Cong Wang <xiyou.wangc...@gmail.com>
---

Note that the motivation for this patch is found in the following discussion:
https://www.spinics.net/lists/netdev/msg501061.html
---
 tc/m_skbedit.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/tc/m_skbedit.c b/tc/m_skbedit.c
index 7391fc7f..59b2affc 100644
--- a/tc/m_skbedit.c
+++ b/tc/m_skbedit.c
@@ -30,16 +30,18 @@
 
 static void explain(void)
 {
-       fprintf(stderr, "Usage: ... skbedit <[QM] [PM] [MM] [PT]>\n"
+       fprintf(stderr, "Usage: ... skbedit <[QM] [PM] [MM] [PT] [IF]>\n"
                "QM = queue_mapping QUEUE_MAPPING\n"
                "PM = priority PRIORITY\n"
                "MM = mark MARK\n"
                "PT = ptype PACKETYPE\n"
+               "IF = inheritdsfield\n"
                "PACKETYPE = is one of:\n"
                "  host, otherhost, broadcast, multicast\n"
                "QUEUE_MAPPING = device transmit queue to use\n"
                "PRIORITY = classID to assign to priority field\n"
-               "MARK = firewall mark to set\n");
+               "MARK = firewall mark to set\n"
+               "note: inheritdsfield maps DS field to skb->priority\n");
 }
 
 static void
@@ -60,6 +62,7 @@ parse_skbedit(struct action_util *a, int *argc_p, char 
***argv_p, int tca_id,
        unsigned int tmp;
        __u16 queue_mapping, ptype;
        __u32 flags = 0, priority, mark;
+       __u64 pure_flags = 0;
        struct tc_skbedit sel = { 0 };
 
        if (matches(*argv, "skbedit") != 0)
@@ -111,6 +114,9 @@ parse_skbedit(struct action_util *a, int *argc_p, char 
***argv_p, int tca_id,
                        }
                        flags |= SKBEDIT_F_PTYPE;
                        ok++;
+               } else if (matches(*argv, "inheritdsfield") == 0) {
+                       pure_flags |= SKBEDIT_F_INHERITDSFIELD;
+                       ok++;
                } else if (matches(*argv, "help") == 0) {
                        usage();
                } else {
@@ -156,6 +162,9 @@ parse_skbedit(struct action_util *a, int *argc_p, char 
***argv_p, int tca_id,
        if (flags & SKBEDIT_F_PTYPE)
                addattr_l(n, MAX_MSG, TCA_SKBEDIT_PTYPE,
                          &ptype, sizeof(ptype));
+       if (pure_flags != 0)
+               addattr_l(n, MAX_MSG, TCA_SKBEDIT_FLAGS,
+                       &pure_flags, sizeof(pure_flags));
        addattr_nest_end(n, tail);
 
        *argc_p = argc;
@@ -214,6 +223,13 @@ static int print_skbedit(struct action_util *au, FILE *f, 
struct rtattr *arg)
                else
                        print_uint(PRINT_ANY, "ptype", " ptype %u", ptype);
        }
+       if (tb[TCA_SKBEDIT_FLAGS] != NULL) {
+               __u64 *flags = RTA_DATA(tb[TCA_SKBEDIT_FLAGS]);
+
+               if (*flags & SKBEDIT_F_INHERITDSFIELD)
+                       print_string(PRINT_ANY, "inheritdsfield", " %s",
+                                    "inheritdsfield");
+       }
 
        print_action_control(f, " ", p->action, "");
 
-- 
2.17.1

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