Re: [PATCH 03/14] Add csum_udp6() helper for calculating UDP over IPv6 checksums

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Oct 18, 2022 at 05:02:31AM +0200, Stefano Brivio wrote:
> On Mon, 17 Oct 2022 19:57:56 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > Add a helper for calculating UDP checksums when used over IPv6
> > For future flexibility, the new helper takes parameters for the fields in
> > the IPv6 pseudo-header, so an IPv6 header or pseudo-header doesn't need to
> > be explicitly constructed.  It also allows the UDP header and payload to
> > be in separate buffers, although we don't use this yet.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  checksum.c | 23 +++++++++++++++++++++++
> >  checksum.h |  5 +++++
> >  tap.c      |  5 ++---
> >  3 files changed, 30 insertions(+), 3 deletions(-)
> > 
> > diff --git a/checksum.c b/checksum.c
> > index c8b6b42..0849fb1 100644
> > --- a/checksum.c
> > +++ b/checksum.c
> > @@ -52,6 +52,7 @@
> >  #include <stddef.h>
> >  #include <stdint.h>
> >  
> > +#include <linux/udp.h>
> >  #include <linux/icmp.h>
> >  #include <linux/icmpv6.h>
> >  
> > @@ -122,6 +123,28 @@ void csum_icmp4(struct icmphdr *icmp4hr, const void *payload, size_t len)
> >  	icmp4hr->checksum = csum_unaligned(payload, len, hrsum);
> >  }
> >  
> > +/**
> > + * csum_udp6() - Calculate checksum for a UDP over IPv6 packet
> 
> Calculate and set.

Done.

> > + * @udp6hr:	UDP header, initialized apart from checksum
> 
> -ised.

Done.

> > + * @payload:	UDP packet payload
> > + * @len:	Length of @payload (not including UDP header)
> > + */
> > +void csum_udp6(struct udphdr *udp6hr,
> > +	       const struct in6_addr *saddr,
> > +	       const struct in6_addr *daddr,
> 
> You could use some horizontal space.

Done.

> > +	       const void *payload, size_t len)
> > +{
> > +	/* Partial checksum for the pseudo-IPv6 header */
> > +	uint32_t psum = sum_16b(saddr, sizeof(*saddr)) +
> > +		sum_16b(daddr, sizeof(*daddr)) +
> > +		htons(len + sizeof(*udp6hr)) + htons(IPPROTO_UDP);
> 
> Alignment:
> 
> 	uint32_t psum = sum_16b(saddr, sizeof(*saddr)) +
> 			sum_16b(daddr, sizeof(*daddr)) +
> 			htons(len + sizeof(*udp6hr))   + htons(IPPROTO_UDP);

Done.

> > +	udp6hr->check = 0;
> > +	/* Add in partial checksum for the UDP header alone */
> > +	psum += sum_16b(udp6hr, sizeof(*udp6hr));
> > +	udp6hr->check = csum_unaligned(payload, len, psum);
> > +}
> > +
> >  /**
> >   * csum_icmp6() - Calculate checksum for an ICMPv6 packet
> >   * @icmp6hr:	ICMPv6 header, initialized apart from checksum
> > diff --git a/checksum.h b/checksum.h
> > index ff95cf9..1b9f48e 100644
> > --- a/checksum.h
> > +++ b/checksum.h
> > @@ -6,6 +6,7 @@
> >  #ifndef CHECKSUM_H
> >  #define CHECKSUM_H
> >  
> > +struct udphdr;
> >  struct icmphdr;
> >  struct icmp6hdr;
> >  
> > @@ -13,6 +14,10 @@ uint32_t sum_16b(const void *buf, size_t len);
> >  uint16_t csum_fold(uint32_t sum);
> >  uint16_t csum_unaligned(const void *buf, size_t len, uint32_t init);
> >  void csum_icmp4(struct icmphdr *ih, const void *payload, size_t len);
> > +void csum_udp6(struct udphdr *udp6hr,
> > +	       const struct in6_addr *saddr,
> > +	       const struct in6_addr *daddr,
> > +	       const void *payload, size_t len);
> 
> Use some horizontal space.

Done.

> >  void csum_icmp6(struct icmp6hdr *ih,
> >  		const struct in6_addr *saddr,
> >  		const struct in6_addr *daddr,
> > diff --git a/tap.c b/tap.c
> > index f082901..9c197cb 100644
> > --- a/tap.c
> > +++ b/tap.c
> > @@ -183,9 +183,8 @@ void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto,
> >  		} else if (proto == IPPROTO_UDP) {
> >  			struct udphdr *uh = (struct udphdr *)(ip6h + 1);
> >  
> > -			uh->check = 0;
> > -			uh->check = csum_unaligned(ip6h, len + sizeof(*ip6h),
> > -						   0);
> > +			csum_udp6(uh, &ip6h->saddr, &ip6h->daddr,
> > +				  uh + 1, len - sizeof(*uh));
> >  		} else if (proto == IPPROTO_ICMPV6) {
> >  			struct icmp6hdr *ih = (struct icmp6hdr *)(ip6h + 1);
> >  
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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