diff options
author | Phil Sutter <phil@nwl.cc> | 2020-10-27 17:05:25 +0100 |
---|---|---|
committer | Phil Sutter <phil@nwl.cc> | 2020-11-04 14:44:02 +0100 |
commit | 8a927c56d83ed0f78785011bd92a53edc25a0ca0 (patch) | |
tree | ca0858a00457cefcc3e636b0b102990250e51e0a | |
parent | a51a0bec1f698b9980a266e2393d3f80596bbae0 (diff) |
src: Support odd-sized payload matches
When expanding a payload match, don't disregard oversized templates at
the right offset. A more flexible user may extract less bytes from the
packet if only parts of a field are interesting, e.g. only the prefix of
source/destination address. Support that by using the template, but fix
the length. Later when creating a relational expression for it, detect
the unusually small payload expression length and turn the RHS value
into a prefix expression.
Signed-off-by: Phil Sutter <phil@nwl.cc>
-rw-r--r-- | src/netlink_delinearize.c | 6 | ||||
-rw-r--r-- | src/payload.c | 5 |
2 files changed, 11 insertions, 0 deletions
diff --git a/src/netlink_delinearize.c b/src/netlink_delinearize.c index 43d7ff82..b7876a8d 100644 --- a/src/netlink_delinearize.c +++ b/src/netlink_delinearize.c @@ -1776,6 +1776,12 @@ static void payload_match_expand(struct rule_pp_ctx *ctx, tmp = constant_expr_splice(right, left->len); expr_set_type(tmp, left->dtype, left->byteorder); + if (left->payload.tmpl && (left->len < left->payload.tmpl->len)) { + mpz_lshift_ui(tmp->value, left->payload.tmpl->len - left->len); + tmp->len = left->payload.tmpl->len; + tmp = prefix_expr_alloc(&tmp->location, tmp, left->len); + } + nexpr = relational_expr_alloc(&expr->location, expr->op, left, tmp); if (expr->op == OP_EQ) diff --git a/src/payload.c b/src/payload.c index ca422d5b..e51c5797 100644 --- a/src/payload.c +++ b/src/payload.c @@ -822,6 +822,11 @@ void payload_expr_expand(struct list_head *list, struct expr *expr, expr->payload.offset += tmpl->len; if (expr->len == 0) return; + } else if (expr->len > 0) { + new = payload_expr_alloc(&expr->location, desc, i); + new->len = expr->len; + list_add_tail(&new->list, list); + return; } else break; } |