[iproute PATCH v2 2/4] tc: pedit: Fix for big-endian systems

[Phil Sutter]

This was tricky to get right:
- The 'stride' value used for 8 and 16 bit values must behave inverse to
  the value's intra word offset to work correctly with big-endian data
  act_pedit is editing.
- The 'm' array's values are in host byte order, so they have to be
  converted as well (and the ordering was just inverse, for some
  reason).
- The only sane way of getting this right is to manipulate value/mask in
  host byte order and convert the output.
- TIPV4 (i.e. 'munge ip src/dst') had it's own pitfall: the address
  parser converts to network byte order automatically. This patch fixes
  this by converting it back before calling pack_key32, which is a hack
  but at least does not require to implement a completely separate code
  flow.

Signed-off-by: Phil Sutter <p...@nwl.cc>
---
 tc/m_pedit.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/tc/m_pedit.c b/tc/m_pedit.c
index ca78a83dd9d9d..30a6f3673e896 100644
--- a/tc/m_pedit.c
+++ b/tc/m_pedit.c
@@ -156,7 +156,7 @@ int
 pack_key16(__u32 retain, struct tc_pedit_sel *sel, struct tc_pedit_key *tkey)
 {
        int ind, stride;
-       __u32 m[4] = {0xFFFF0000, 0xFF0000FF, 0x0000FFFF};
+       __u32 m[4] = {0x0000FFFF, 0xFF0000FF, 0xFFFF0000};
 
        if (tkey->val > 0xFFFF || tkey->mask > 0xFFFF) {
                fprintf(stderr, "pack_key16 bad value\n");
@@ -170,9 +170,9 @@ pack_key16(__u32 retain, struct tc_pedit_sel *sel, struct 
tc_pedit_key *tkey)
                return -1;
        }
 
-       stride = 8 * ind;
-       tkey->val = htons(tkey->val & retain) << stride;
-       tkey->mask = (htons(tkey->mask | ~retain) << stride) | m[ind];
+       stride = 8 * (2 - ind);
+       tkey->val = htonl((tkey->val & retain) << stride);
+       tkey->mask = htonl(((tkey->mask | ~retain) << stride) | m[ind]);
 
        tkey->off &= ~3;
 
@@ -186,7 +186,7 @@ int
 pack_key8(__u32 retain, struct tc_pedit_sel *sel, struct tc_pedit_key *tkey)
 {
        int ind, stride;
-       __u32 m[4] = {0xFFFFFF00, 0xFFFF00FF, 0xFF00FFFF, 0x00FFFFFF};
+       __u32 m[4] = {0x00FFFFFF, 0xFF00FFFF, 0xFFFF00FF, 0xFFFFFF00};
 
        if (tkey->val > 0xFF || tkey->mask > 0xFF) {
                fprintf(stderr, "pack_key8 bad value (val %x mask %x\n", 
tkey->val, tkey->mask);
@@ -195,9 +195,9 @@ pack_key8(__u32 retain, struct tc_pedit_sel *sel, struct 
tc_pedit_key *tkey)
 
        ind = tkey->off & 3;
 
-       stride = 8 * ind;
-       tkey->val = (tkey->val & retain) << stride;
-       tkey->mask = ((tkey->mask | ~retain) << stride) | m[ind];
+       stride = 8 * (3 - ind);
+       tkey->val = htonl((tkey->val & retain) << stride);
+       tkey->mask = htonl(((tkey->mask | ~retain) << stride) | m[ind]);
 
        tkey->off &= ~3;
 
@@ -283,6 +283,9 @@ parse_cmd(int *argc_p, char ***argv_p, __u32 len, int type, 
__u32 retain, struct
        tkey->val = val;
        tkey->mask = mask;
 
+       if (type == TIPV4)
+               tkey->val = ntohl(tkey->val);
+
        if (len == 1) {
                res = pack_key8(retain, sel, tkey);
                goto done;
-- 
2.7.2