git: b891f61ef538 - main - if_wg: fix erroneous calculation in calculate_padding() for p_mtu == 0

The branch main has been updated by kevans:

URL: https://cgit.FreeBSD.org/src/commit/?id=b891f61ef538a4e9b4658b4b756635c8036a5788

commit b891f61ef538a4e9b4658b4b756635c8036a5788
Author:     Aaron LI <aly@aaronly.me>
AuthorDate: 2024-01-17 23:29:23 +0000
Commit:     Kyle Evans <kevans@FreeBSD.org>
CommitDate: 2024-01-17 23:29:52 +0000

    if_wg: fix erroneous calculation in calculate_padding() for p_mtu == 0
    
    In practice this is harmless; only keepalive packets may realistically have
    p_mtu == 0, and they'll also have no payload so the math works out the same
    either way.  Still, let's prefer technical accuracy and calculate the amount
    of padding needed rather than the padded length...
    
    PR:             276363
---
 sys/dev/wg/if_wg.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/sys/dev/wg/if_wg.c b/sys/dev/wg/if_wg.c
index 71c80c8b5f77..58c0e2db1ee8 100644
--- a/sys/dev/wg/if_wg.c
+++ b/sys/dev/wg/if_wg.c
@@ -1463,8 +1463,12 @@ calculate_padding(struct wg_packet *pkt)
 {
 	unsigned int padded_size, last_unit = pkt->p_mbuf->m_pkthdr.len;
 
-	if (__predict_false(!pkt->p_mtu))
-		return (last_unit + (WG_PKT_PADDING - 1)) & ~(WG_PKT_PADDING - 1);
+	/* Keepalive packets don't set p_mtu, but also have a length of zero. */
+	if (__predict_false(pkt->p_mtu == 0)) {
+		padded_size = (last_unit + (WG_PKT_PADDING - 1)) &
+		    ~(WG_PKT_PADDING - 1);
+		return (padded_size - last_unit);
+	}
 
 	if (__predict_false(last_unit > pkt->p_mtu))
 		last_unit %= pkt->p_mtu;
@@ -1472,7 +1476,7 @@ calculate_padding(struct wg_packet *pkt)
 	padded_size = (last_unit + (WG_PKT_PADDING - 1)) & ~(WG_PKT_PADDING - 1);
 	if (pkt->p_mtu < padded_size)
 		padded_size = pkt->p_mtu;
-	return padded_size - last_unit;
+	return (padded_size - last_unit);
 }
 
 static void