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ofp-actions: Make ofpact_finish() harder to misuse.
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It's pretty easy to forget to update the pointer to an ofpact when
finishing it.  This commit forces the caller to pass a pointer-to-pointer
instead, and uses that to automatically update the pointer.  There still
could be cases that retain other pointers into the ofpbuf, but I imagine
that this is harder to misuse.

Suggested-by: Joe Stringer <joe@ovn.org>
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Joe Stringer <joe@ovn.org>
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@blp
blp committed Apr 13, 2016
1 parent 6e3a764 commit ce05810
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Showing 6 changed files with 42 additions and 22 deletions.
2 changes: 1 addition & 1 deletion lib/bundle.c
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Original file line number Diff line number Diff line change
Expand Up @@ -179,7 +179,7 @@ bundle_parse__(const char *s, char **save_ptr,
bundle = ofpacts->header;
bundle->n_slaves++;
}
bundle = ofpact_finish(ofpacts, &bundle->ofpact);
ofpact_finish_BUNDLE(ofpacts, &bundle);
bundle->basis = atoi(basis);

if (!strcasecmp(fields, "eth_src")) {
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2 changes: 1 addition & 1 deletion lib/learn.c
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Original file line number Diff line number Diff line change
Expand Up @@ -380,7 +380,7 @@ learn_parse__(char *orig, char *arg, struct ofpbuf *ofpacts)
}
}
}
ofpact_finish(ofpacts, &learn->ofpact);
ofpact_finish_LEARN(ofpacts, &learn);

return NULL;
}
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34 changes: 19 additions & 15 deletions lib/ofp-actions.c
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Original file line number Diff line number Diff line change
Expand Up @@ -668,7 +668,7 @@ decode_NXAST_RAW_CONTROLLER(const struct nx_action_controller *nac,
oc->max_len = ntohs(nac->max_len);
oc->controller_id = ntohs(nac->controller_id);
oc->reason = nac->reason;
ofpact_finish(out, &oc->ofpact);
ofpact_finish_CONTROLLER(out, &oc);

return 0;
}
Expand Down Expand Up @@ -737,7 +737,7 @@ decode_NXAST_RAW_CONTROLLER2(const struct nx_action_controller2 *nac2,
}
}

ofpact_finish(out, &oc->ofpact);
ofpact_finish_CONTROLLER(out, &oc);

return 0;
}
Expand Down Expand Up @@ -852,7 +852,7 @@ parse_CONTROLLER(char *arg, struct ofpbuf *ofpacts,
controller = ofpacts->header;
controller->userdata_len = userdata_len;
}
ofpact_finish(ofpacts, &controller->ofpact);
ofpact_finish_CONTROLLER(ofpacts, &controller);
}

return NULL;
Expand Down Expand Up @@ -1262,7 +1262,7 @@ decode_bundle(bool load, const struct nx_action_bundle *nab,
bundle = ofpacts->header;
}

bundle = ofpact_finish(ofpacts, &bundle->ofpact);
ofpact_finish_BUNDLE(ofpacts, &bundle);
if (!error) {
error = bundle_check(bundle, OFPP_MAX, NULL);
}
Expand Down Expand Up @@ -3096,7 +3096,7 @@ decode_OFPAT_RAW_DEC_NW_TTL(struct ofpbuf *out)
ids->n_controllers = 1;
ofpbuf_put(out, &id, sizeof id);
ids = out->header;
ofpact_finish(out, &ids->ofpact);
ofpact_finish_DEC_TTL(out, &ids);
return error;
}

Expand Down Expand Up @@ -3133,7 +3133,7 @@ decode_NXAST_RAW_DEC_TTL_CNT_IDS(const struct nx_action_cnt_ids *nac_ids,
ids = out->header;
}

ofpact_finish(out, &ids->ofpact);
ofpact_finish_DEC_TTL(out, &ids);

return 0;
}
Expand Down Expand Up @@ -3172,7 +3172,7 @@ parse_noargs_dec_ttl(struct ofpbuf *ofpacts)
ofpbuf_put(ofpacts, &id, sizeof id);
ids = ofpacts->header;
ids->n_controllers++;
ofpact_finish(ofpacts, &ids->ofpact);
ofpact_finish_DEC_TTL(ofpacts, &ids);
}

static char * OVS_WARN_UNUSED_RESULT
Expand All @@ -3199,7 +3199,7 @@ parse_DEC_TTL(char *arg, struct ofpbuf *ofpacts,
return xstrdup("dec_ttl_cnt_ids: expected at least one controller "
"id.");
}
ofpact_finish(ofpacts, &ids->ofpact);
ofpact_finish_DEC_TTL(ofpacts, &ids);
}
return NULL;
}
Expand Down Expand Up @@ -4228,7 +4228,7 @@ decode_NXAST_RAW_LEARN(const struct nx_action_learn *nal,
get_subfield(spec->n_bits, &p, &spec->dst);
}
}
ofpact_finish(ofpacts, &learn->ofpact);
ofpact_finish_LEARN(ofpacts, &learn);

if (!is_all_zeros(p, (char *) end - (char *) p)) {
return OFPERR_OFPBAC_BAD_ARGUMENT;
Expand Down Expand Up @@ -4554,7 +4554,7 @@ decode_NXAST_RAW_NOTE(const struct nx_action_note *nan,
note = ofpact_put_NOTE(out);
note->length = length;
ofpbuf_put(out, nan->note, length);
ofpact_finish(out, out->header);
ofpact_finish_NOTE(out, &note);

return 0;
}
Expand Down Expand Up @@ -4586,7 +4586,7 @@ parse_NOTE(const char *arg, struct ofpbuf *ofpacts,
struct ofpact_note *note = ofpbuf_at_assert(ofpacts, start_ofs,
sizeof *note);
note->length = ofpacts->size - (start_ofs + sizeof *note);
ofpact_finish(ofpacts, &note->ofpact);
ofpact_finish_NOTE(ofpacts, &note);
return NULL;
}

Expand Down Expand Up @@ -4994,7 +4994,7 @@ decode_NXAST_RAW_CT(const struct nx_action_conntrack *nac,

conntrack = ofpbuf_push_uninit(out, sizeof(*conntrack));
out->header = &conntrack->ofpact;
conntrack = ofpact_finish(out, &conntrack->ofpact);
ofpact_finish_CT(out, &conntrack);

if (conntrack->ofpact.len > sizeof(*conntrack)
&& !(conntrack->flags & NX_CT_F_COMMIT)) {
Expand Down Expand Up @@ -5115,7 +5115,7 @@ parse_CT(char *arg, struct ofpbuf *ofpacts,
}
}

ofpact_finish(ofpacts, &oc->ofpact);
ofpact_finish_CT(ofpacts, &oc);
ofpbuf_push_uninit(ofpacts, ct_offset);
return error;
}
Expand Down Expand Up @@ -7419,6 +7419,7 @@ ofpacts_format(const struct ofpact *ofpacts, size_t ofpacts_len,

/* Internal use by helpers. */

/* Implementation of ofpact_put_<ENUM>(). */
void *
ofpact_put(struct ofpbuf *ofpacts, enum ofpact_type type, size_t len)
{
Expand All @@ -7430,6 +7431,7 @@ ofpact_put(struct ofpbuf *ofpacts, enum ofpact_type type, size_t len)
return ofpact;
}

/* Implementation of ofpact_init_<ENUM>(). */
void
ofpact_init(struct ofpact *ofpact, enum ofpact_type type, size_t len)
{
Expand All @@ -7438,8 +7440,10 @@ ofpact_init(struct ofpact *ofpact, enum ofpact_type type, size_t len)
ofpact->raw = -1;
ofpact->len = len;
}

/* Finishes composing a variable-length action (begun using

/* Implementation of ofpact_finish_<ENUM>().
*
* Finishes composing a variable-length action (begun using
* ofpact_put_<NAME>()), by padding the action to a multiple of OFPACT_ALIGNTO
* bytes and updating its embedded length field. See the large comment near
* the end of ofp-actions.h for more information.
Expand Down
22 changes: 19 additions & 3 deletions lib/ofp-actions.h
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Original file line number Diff line number Diff line change
Expand Up @@ -903,6 +903,7 @@ const char *ofpact_name(enum ofpact_type);
/* Internal use by the helpers below. */
void ofpact_init(struct ofpact *, enum ofpact_type, size_t len);
void *ofpact_put(struct ofpbuf *, enum ofpact_type, size_t len);
void *ofpact_finish(struct ofpbuf *, struct ofpact *);

/* For each OFPACT_<ENUM> with a corresponding struct <STRUCT>, this defines
* the following commonly useful functions:
Expand All @@ -924,6 +925,16 @@ void *ofpact_put(struct ofpbuf *, enum ofpact_type, size_t len);
* Returns 'ofpact' cast to "struct <STRUCT> *". 'ofpact->type' must be
* OFPACT_<ENUM>.
*
* void ofpact_finish_<ENUM>(struct ofpbuf *ofpacts, struct <STRUCT> **ap);
*
* Finishes composing variable-length action '*ap' (begun using
* ofpact_put_<NAME>() on 'ofpacts'), by padding the action to a multiple
* of OFPACT_ALIGNTO bytes and updating its embedded length field.
*
* May reallocate 'ofpacts', and so as a convenience automatically updates
* '*ap' to point to the new location. If the caller has other pointers
* within 'ap' or 'ofpacts', it needs to update them manually.
*
* as well as the following more rarely useful definitions:
*
* void ofpact_init_<ENUM>(struct <STRUCT> *ofpact);
Expand Down Expand Up @@ -965,13 +976,18 @@ void *ofpact_put(struct ofpbuf *, enum ofpact_type, size_t len);
{ \
ofpact_init(&ofpact->ofpact, OFPACT_##ENUM, \
OFPACT_##ENUM##_SIZE); \
} \
\
static inline void \
ofpact_finish_##ENUM(struct ofpbuf *ofpbuf, struct STRUCT **ofpactp) \
{ \
struct ofpact *ofpact = &(*ofpactp)->ofpact; \
ovs_assert(ofpact->type == OFPACT_##ENUM); \
*ofpactp = ofpact_finish(ofpbuf, ofpact); \
}
OFPACTS
#undef OFPACT

/* Call after adding the variable-length part to a variable-length action. */
void *ofpact_finish(struct ofpbuf *, struct ofpact *);

/* Additional functions for composing ofpacts. */
struct ofpact_set_field *ofpact_put_reg_load(struct ofpbuf *ofpacts);

Expand Down
2 changes: 1 addition & 1 deletion ofproto/ofproto-dpif.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1411,7 +1411,7 @@ add_internal_flows(struct ofproto_dpif *ofproto)
controller->max_len = UINT16_MAX;
controller->controller_id = 0;
controller->reason = OFPR_IMPLICIT_MISS;
controller = ofpact_finish(&ofpacts, &controller->ofpact);
ofpact_finish_CONTROLLER(&ofpacts, &controller);

error = add_internal_miss_flow(ofproto, id++, &ofpacts,
&ofproto->miss_rule);
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2 changes: 1 addition & 1 deletion ovn/lib/actions.c
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Original file line number Diff line number Diff line change
Expand Up @@ -205,7 +205,7 @@ finish_controller_op(struct ofpbuf *ofpacts, size_t ofs)
struct ofpact_controller *oc = ofpbuf_at_assert(ofpacts, ofs, sizeof *oc);
ofpacts->header = oc;
oc->userdata_len = ofpacts->size - (ofs + sizeof *oc);
ofpact_finish(ofpacts, &oc->ofpact);
ofpact_finish_CONTROLLER(ofpacts, &oc);
}

static void
Expand Down

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