tc: pedit: add decrement operation

Implement a decrement operation for ttl and hoplimit.

Since this is just syntactic sugar, it goes that:

  tc filter add ... action pedit ex munge ip ttl dec ...
  tc filter add ... action pedit ex munge ip6 hoplimit dec ...

is just a more readable version of this:

  tc filter add ... action pedit ex munge ip ttl add 0xff ...
  tc filter add ... action pedit ex munge ip6 hoplimit add 0xff ...

This feature was suggested by some pseudo tc examples in Mellanox's
documentation[1], but wasn't present in neither their mlnx-iproute2
nor iproute2.

Tested with skip_sw on Mellanox ConnectX-6 Dx.

[1] https://docs.mellanox.com/pages/viewpage.action?pageId=47033989

v3:
   - Use dedicated flags argument in parse_cmd() (David Ahern)
   - Minor rewording of the man page

v2:
   - Fix whitespace issue (Stephen Hemminger)
   - Add to usage info in explain()

Signed-off-by: Asbjørn Sloth Tønnesen <asbjorn@asbjorn.st>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David Ahern <dsahern@kernel.org>

diff --git a/man/man8/tc-pedit.8 b/man/man8/tc-pedit.8
index 376ad4a8e7d1f0ae8ca97aa4d3ee5cf7842d10e4..15159ddd01e94995f18dfd2ffeb08976d3c30180 100644 (file)
--- a/man/man8/tc-pedit.8
+++ b/man/man8/tc-pedit.8
@@ -77,6 +77,7 @@ pedit - generic packet editor action
 .IR VAL " | "
 .BR add
 .IR VAL " | "
+.BR decrement " | "
 .BR preserve " } [ " retain
 .IR RVAL " ]"
 
@@ -96,7 +97,7 @@ chosen automatically based on the header field size.
 .B ex
 Use extended pedit.
 .I EXTENDED_LAYERED_OP
-and the add
+and the add/decrement
 .I CMD_SPEC
 are allowed only in this mode.
 .TP
@@ -288,6 +289,11 @@ is defined by the size of the addressed header field in
 .IR EXTENDED_LAYERED_OP .
 This operation is supported only for extended layered op.
 .TP
+.BI decrement
+Decrease the addressed data by one.
+This operation is supported only for
+.BR ip " " ttl " and " ip6 " " hoplimit "."
+.TP
 .B preserve
 Keep the addressed data as is.
 .TP

diff --git a/tc/m_pedit.c b/tc/m_pedit.c
index b745c3793245bb098dff5a1c11c545b3b04622be..54949e4319536ff309c46c2e187b2c56afb3e65a 100644 (file)
--- a/tc/m_pedit.c
+++ b/tc/m_pedit.c
@@ -41,7 +41,7 @@ static void explain(void)
                "\t\tATC:= at <atval> offmask <maskval> shift <shiftval>\n"
                "\t\tNOTE: offval is byte offset, must be multiple of 4\n"
                "\t\tNOTE: maskval is a 32 bit hex number\n \t\tNOTE: shiftval is a shift value\n"
-               "\t\tCMD:= clear | invert | set <setval>| add <addval> | retain\n"
+               "\t\tCMD:= clear | invert | set <setval> | add <addval> | decrement | retain\n"
                "\t<LAYERED>:= ip <ipdata> | ip6 <ip6data>\n"
                " \t\t| udp <udpdata> | tcp <tcpdata> | icmp <icmpdata>\n"
                "\tCONTROL:= reclassify | pipe | drop | continue | pass |\n"
@@ -360,15 +360,24 @@ int parse_cmd(int *argc_p, char ***argv_p, __u32 len, int type, __u32 retain,
                if (matches(*argv, "add") == 0)
                        tkey->cmd = TCA_PEDIT_KEY_EX_CMD_ADD;
 
-               if (!sel->extended && tkey->cmd) {
-                       fprintf(stderr,
-                               "Non extended mode. only 'set' command is supported\n");
-                       return -1;
-               }
+               if (!sel->extended && tkey->cmd)
+                       goto non_ext_only_set_cmd;
 
                NEXT_ARG();
                if (parse_val(&argc, &argv, val, type))
                        return -1;
+       } else if (matches(*argv, "decrement") == 0) {
+               if ((flags & PEDIT_ALLOW_DEC) == 0) {
+                       fprintf(stderr,
+                               "decrement command is not supported for this field\n");
+                       return -1;
+               }
+
+               if (!sel->extended)
+                       goto non_ext_only_set_cmd;
+
+               tkey->cmd = TCA_PEDIT_KEY_EX_CMD_ADD;
+               *v = retain; /* decrement by overflow */
        } else if (matches(*argv, "preserve") == 0) {
                retain = 0;
        } else {
@@ -431,6 +440,10 @@ done:
        *argv_p = argv;
        return res;
 
+non_ext_only_set_cmd:
+       fprintf(stderr,
+               "Non extended mode. only 'set' command is supported\n");
+       return -1;
 }
 
 static int parse_offset(int *argc_p, char ***argv_p, struct m_pedit_sel *sel,

diff --git a/tc/m_pedit.h b/tc/m_pedit.h
index 7398f66d7a2295f64ce8f9933886d54916b07b0e..549bcf86a91fc2f80fff0355d4b4d56219a800e2 100644 (file)
--- a/tc/m_pedit.h
+++ b/tc/m_pedit.h
@@ -39,6 +39,10 @@
 
 #define PEDITKINDSIZ 16
 
+enum m_pedit_flags {
+       PEDIT_ALLOW_DEC = 1<<0,
+};
+
 struct m_pedit_key {
        __u32           mask;  /* AND */
        __u32           val;   /*XOR */

diff --git a/tc/p_ip.c b/tc/p_ip.c
index 2d1643d0be3f092b42305278fa4f619125e4f6a2..8eed9e8da57dc275df7a6c2d7a7633b148570d86 100644 (file)
--- a/tc/p_ip.c
+++ b/tc/p_ip.c
@@ -68,7 +68,7 @@ parse_ip(int *argc_p, char ***argv_p,
        if (strcmp(*argv, "ttl") == 0) {
                NEXT_ARG();
                tkey->off = 8;
-               res = parse_cmd(&argc, &argv, 1, TU32, RU8, sel, tkey, 0);
+               res = parse_cmd(&argc, &argv, 1, TU32, RU8, sel, tkey, PEDIT_ALLOW_DEC);
                goto done;
        }
        if (strcmp(*argv, "protocol") == 0) {

diff --git a/tc/p_ip6.c b/tc/p_ip6.c
index f9d5d3b02b54d90ce838067e1f7833f3bb534b0b..f855c59e1f6ba2e5124adf0b2c7f2cff201971eb 100644 (file)
--- a/tc/p_ip6.c
+++ b/tc/p_ip6.c
@@ -71,7 +71,7 @@ parse_ip6(int *argc_p, char ***argv_p,
        if (strcmp(*argv, "hoplimit") == 0) {
                NEXT_ARG();
                tkey->off = 7;
-               res = parse_cmd(&argc, &argv, 1, TU32, RU8, sel, tkey, 0);
+               res = parse_cmd(&argc, &argv, 1, TU32, RU8, sel, tkey, PEDIT_ALLOW_DEC);
                goto done;
        }
        if (strcmp(*argv, "traffic_class") == 0) {