git: aa64a8f5c35c - main - udplite: fix checksum computation on the sender side

[Michael Tuexen]

The branch main has been updated by tuexen:

URL: https://cgit.FreeBSD.org/src/commit/?id=aa64a8f5c35c13b1c325f1a4597c987a37bec5da

commit aa64a8f5c35c13b1c325f1a4597c987a37bec5da
Author: Michael Tuexen <tue...@FreeBSD.org>
AuthorDate: 2023-11-01 09:24:56 +0000
Commit: Michael Tuexen <tue...@FreeBSD.org>
CommitDate: 2023-11-01 09:24:56 +0000

udplite: fix checksum computation on the sender side

Don't fill the fields of the UDP/IP header not used for the
checksum computation before performing the checksum computation.

Reviewed by: glebius
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D42275
---
sys/netinet/udp_usrreq.c | 29 +++++++++++++++--------------
1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/sys/netinet/udp_usrreq.c b/sys/netinet/udp_usrreq.c
index cbda7f536262..a96ec22c5992 100644
--- a/sys/netinet/udp_usrreq.c
+++ b/sys/netinet/udp_usrreq.c
@@ -1330,8 +1330,12 @@ udp_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *addr,
* into network format.
*/
ui = mtod(m, struct udpiphdr *);
- bzero(ui->ui_x1, sizeof(ui->ui_x1)); /* XXX still needed? */
- ui->ui_v = IPVERSION << 4;
+ /*
+ * Filling only those fields of udpiphdr that participate in the
+ * checksum calculation. The rest must be zeroed and will be filled
+ * later.
+ */
+ bzero(ui->ui_x1, sizeof(ui->ui_x1));
ui->ui_pr = pr;
ui->ui_src = laddr;
ui->ui_dst = faddr;
@@ -1356,16 +1360,6 @@ udp_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *addr,
cscov_partial = (cscov == 0) ? 0 : 1;
}

- /*
- * Set the Don't Fragment bit in the IP header.
- */
- if (inp->inp_flags & INP_DONTFRAG) {
- struct ip *ip;
-
- ip = (struct ip *)&ui->ui_i;
- ip->ip_off |= htons(IP_DF);
- }
-
if (inp->inp_socket->so_options & SO_DONTROUTE)
ipflags |= IP_ROUTETOIF;
if (inp->inp_socket->so_options & SO_BROADCAST)
@@ -1399,9 +1393,16 @@ udp_send(struct socket *so, int flags, struct mbuf *m, struct sockaddr *addr,
m->m_pkthdr.csum_flags = CSUM_UDP;
m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
}
+ /*
+ * After finishing the checksum computation, fill the remaining fields
+ * of udpiphdr.
+ */
+ ((struct ip *)ui)->ip_v = IPVERSION;
+ ((struct ip *)ui)->ip_tos = tos;
((struct ip *)ui)->ip_len = htons(sizeof(struct udpiphdr) + len);
- ((struct ip *)ui)->ip_ttl = inp->inp_ip_ttl; /* XXX */
- ((struct ip *)ui)->ip_tos = tos; /* XXX */
+ if (inp->inp_flags & INP_DONTFRAG)
+ ((struct ip *)ui)->ip_off |= htons(IP_DF);
+ ((struct ip *)ui)->ip_ttl = inp->inp_ip_ttl;
UDPSTAT_INC(udps_opackets);

/*