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Add a knob to allow zero UDP checksums for UDP/IPv6 traffic on the given UDP port.

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This will be used by some upcoming changes to if_vxlan(4).  RFC 7348 (VXLAN)
says that the UDP checksum "SHOULD be transmitted as zero.  When a packet is
received with a UDP checksum of zero, it MUST be accepted for decapsulation."
But the original IPv6 RFCs did not allow zero UDP checksum.  RFC 6935 attempts
to resolve this.

Reviewed by:	kib@
Sponsored by:	Chelsio Communications
Differential Revision:	https://reviews.freebsd.org/D25873
This commit is contained in:
Navdeep Parhar 2020-09-18 02:21:15 +00:00
parent 830edb4561
commit 72cc43df17
2 changed files with 17 additions and 1 deletions
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3
sys/netinet/udp_var.h
View file

@ -154,6 +154,9 @@ VNET_DECLARE(int, udp_log_in_vain);
#define V_udp_blackhole VNET(udp_blackhole)
#define V_udp_log_in_vain VNET(udp_log_in_vain)
VNET_DECLARE(int, zero_checksum_port);
#define V_zero_checksum_port VNET(zero_checksum_port)
static __inline struct inpcbinfo *
udp_get_inpcbinfo(int protocol)
{

15
sys/netinet6/udp6_usrreq.c
View file

@ -124,6 +124,11 @@ __FBSDID("$FreeBSD$");
#include <security/mac/mac_framework.h>
VNET_DEFINE(int, zero_checksum_port) = 0;
#define V_zero_checksum_port VNET(zero_checksum_port)
SYSCTL_INT(_net_inet6_udp6, OID_AUTO, rfc6935_port, CTLFLAG_VNET | CTLFLAG_RW,
&VNET_NAME(zero_checksum_port), 0,
"Zero UDP checksum allowed for traffic to/from this port.");
/*
* UDP protocol implementation.
* Per RFC 768, August, 1980.
@ -267,7 +272,14 @@ udp6_input(struct mbuf **mp, int *offp, int proto)
}
if (uh->uh_sum == 0) {
UDPSTAT_INC(udps_nosum);
goto badunlocked;
/*
* dport 0 was rejected earlier so this is OK even if
* zero_checksum_port is 0 (which is its default value).
*/
if (ntohs(uh->uh_dport) == V_zero_checksum_port)
goto skip_checksum;
else
goto badunlocked;
}
}
@ -287,6 +299,7 @@ udp6_input(struct mbuf **mp, int *offp, int proto)
goto badunlocked;
}
skip_checksum:
/*
* Construct sockaddr format source address.
*/