git: 055c55abefbe - main - pf: Fix IP checksum on reassembly

[Kristof Provost]

The branch main has been updated by kp:

URL: https://cgit.FreeBSD.org/src/commit/?id=055c55abefbe19fe46a56894595af9c9dad7678c

commit 055c55abefbe19fe46a56894595af9c9dad7678c
Author:     Kristof Provost <kp at FreeBSD.org>
AuthorDate: 2021-04-28 10:56:06 +0000
Commit:     Kristof Provost <kp at FreeBSD.org>
CommitDate: 2021-04-30 06:19:46 +0000

    pf: Fix IP checksum on reassembly
    
    If we reassemble a packet we modify the IP header (to set the length and
    remove the fragment offset information), but we failed to update the
    checksum. On certain setups (mostly where we did not re-fragment again
    afterwards) this could lead to us sending out packets with incorrect
    checksums.
    
    PR:             255432
    MFC after:      1 week
    Sponsored by:   Rubicon Communications, LLC ("Netgate")
    Differential Revision:  https://reviews.freebsd.org/D30026
---
 sys/netpfil/pf/pf_norm.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/sys/netpfil/pf/pf_norm.c b/sys/netpfil/pf/pf_norm.c
index d7310c7bccb4..6de1efa8ff84 100644
--- a/sys/netpfil/pf/pf_norm.c
+++ b/sys/netpfil/pf/pf_norm.c
@@ -794,7 +794,11 @@ pf_reassemble(struct mbuf **m0, struct ip *ip, int dir, u_short *reason)
 	}
 
 	ip = mtod(m, struct ip *);
+	ip->ip_sum = pf_cksum_fixup(ip->ip_sum, ip->ip_len,
+	    htons(hdrlen + total), 0);
 	ip->ip_len = htons(hdrlen + total);
+	ip->ip_sum = pf_cksum_fixup(ip->ip_sum, ip->ip_off,
+	    ip->ip_off & ~(IP_MF|IP_OFFMASK), 0);
 	ip->ip_off &= ~(IP_MF|IP_OFFMASK);
 
 	if (hdrlen + total > IP_MAXPACKET) {