From: Daniel Miller <bonsaiviking@gmail.com>
Date: Tue, 7 Jan 2025 18:11:56 +0000 (-0600)
Subject: Use correct size for VLAN tag load insn
X-Git-Url: https://git.tcpdump.org/libpcap/commitdiff_plain/ffcd5b4ec849395f224da02f29855de3d2c3d330?ds=sidebyside

Use correct size for VLAN tag load insn

Not a true bug, since Linux kernel (net/core/filter.c) forces any load
from SKF_AD_VLAN_TAG to a BPF_H width. However, this change makes
libpcap code easier to understand.
---

diff --git a/gencode.c b/gencode.c
index ecee3755..6b0014ac 100644
--- a/gencode.c
+++ b/gencode.c
@@ -9258,7 +9258,7 @@ gen_vlan_patch_vid_test(compiler_state_t *cstate, struct block *b_vid)
 	sjeq->s.jf = b_vid->stmts;
 	sappend(s, sjeq);
 
-	s2 = new_stmt(cstate, BPF_LD|BPF_B|BPF_ABS);
+	s2 = new_stmt(cstate, BPF_LD|BPF_H|BPF_ABS);
 	s2->s.k = SKF_AD_OFF + SKF_AD_VLAN_TAG;
 	sappend(s, s2);
 	sjeq->s.jt = s2;