Re: [PATCH v3 6/9] checksum: use csum_ip4_header() in udp.c and tcp.c

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

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On Sat, Feb 17, 2024 at 04:07:22PM +0100, Laurent Vivier wrote:
> We can find the same function to compute the IPv4 header
> checksum in tcp.c, udp.c and tap.c
> 
> Use the function defined for tap.c, csum_ip4_header(), but
> with the code used in tcp.c and udp.c as it doesn't need a fully
> initialiazed IPv4 header, only protocol, tot_len, saddr and daddr.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
> 
> Notes:
>     v3:
>       - function parameters provide tot_len, saddr, daddr and protocol
>        rather than an iphdr
>     
>     v2:
>       - use csum_ip4_header() from checksum.c
>       - use code from tcp.c and udp.c in csum_ip4_header()
>       - use "const struct iphfr *", check is not updated by the
>         function but by the caller.
> 
>  checksum.c | 17 +++++++++++++----
>  checksum.h |  3 ++-
>  tap.c      |  3 ++-
>  tcp.c      | 24 +++---------------------
>  udp.c      | 20 ++------------------
>  5 files changed, 22 insertions(+), 45 deletions(-)
> 
> diff --git a/checksum.c b/checksum.c
> index 74e3742bc6f6..511b296a9a80 100644
> --- a/checksum.c
> +++ b/checksum.c
> @@ -57,6 +57,7 @@
>  #include <linux/icmpv6.h>
>  
>  #include "util.h"
> +#include "ip.h"
>  #include "checksum.h"
>  
>  /* Checksums are optional for UDP over IPv4, so we usually just set
> @@ -116,13 +117,21 @@ uint16_t csum_fold(uint32_t sum)
>  uint16_t csum(const void *buf, size_t len, uint32_t init);
>  
>  /**
> - * csum_ip4_header() - Calculate and set IPv4 header checksum
> + * csum_ip4_header() - Calculate IPv4 header checksum
>   * @ip4h:	IPv4 header
>   */
> -void csum_ip4_header(struct iphdr *ip4h)
> +uint16_t csum_ip4_header(uint16_t tot_len, uint8_t protocol,
> +			 uint32_t saddr, uint32_t daddr)
>  {
> -	ip4h->check = 0;
> -	ip4h->check = csum(ip4h, (size_t)ip4h->ihl * 4, 0);
> +	uint32_t sum = L2_BUF_IP4_PSUM(protocol);
> +
> +	sum += tot_len;
> +	sum += (saddr >> 16) & 0xffff;
> +	sum += saddr & 0xffff;
> +	sum += (daddr >> 16) & 0xffff;
> +	sum += daddr & 0xffff;
> +
> +	return ~csum_fold(sum);
>  }
>  
>  /**
> diff --git a/checksum.h b/checksum.h
> index dfa705a04a24..92db73612b6e 100644
> --- a/checksum.h
> +++ b/checksum.h
> @@ -13,7 +13,8 @@ struct icmp6hdr;
>  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_ip4_header(struct iphdr *ip4h);
> +uint16_t csum_ip4_header(uint16_t tot_len, uint8_t protocol,
> +			 uint32_t saddr, uint32_t daddr);
>  void csum_udp4(struct udphdr *udp4hr,
>  	       struct in_addr saddr, struct in_addr daddr,
>  	       const void *payload, size_t len);
> diff --git a/tap.c b/tap.c
> index 3ea03f720d6d..2d590e8525a0 100644
> --- a/tap.c
> +++ b/tap.c
> @@ -160,7 +160,8 @@ static void *tap_push_ip4h(char *buf, struct in_addr src, struct in_addr dst,
>  	ip4h->protocol = proto;
>  	ip4h->saddr = src.s_addr;
>  	ip4h->daddr = dst.s_addr;
> -	csum_ip4_header(ip4h);
> +	ip4h->check = csum_ip4_header(ip4h->tot_len, proto,
> +				      src.s_addr, dst.s_addr);
>  	return ip4h + 1;
>  }
>  
> diff --git a/tcp.c b/tcp.c
> index 45ef5146729a..8887656d3ee8 100644
> --- a/tcp.c
> +++ b/tcp.c
> @@ -934,23 +934,6 @@ static void tcp_sock_set_bufsize(const struct ctx *c, int s)
>  		trace("TCP: failed to set SO_SNDBUF to %i", v);
>  }
>  
> -/**
> - * tcp_update_check_ip4() - Update IPv4 with variable parts from stored one
> - * @buf:	L2 packet buffer with final IPv4 header
> - */
> -static void tcp_update_check_ip4(struct tcp4_l2_buf_t *buf)
> -{
> -	uint32_t sum = L2_BUF_IP4_PSUM(IPPROTO_TCP);
> -
> -	sum += buf->iph.tot_len;
> -	sum += (buf->iph.saddr >> 16) & 0xffff;
> -	sum += buf->iph.saddr & 0xffff;
> -	sum += (buf->iph.daddr >> 16) & 0xffff;
> -	sum += buf->iph.daddr & 0xffff;
> -
> -	buf->iph.check = (uint16_t)~csum_fold(sum);
> -}
> -
>  /**
>   * tcp_update_check_tcp4() - Update TCP checksum from stored one
>   * @buf:	L2 packet buffer with final IPv4 header
> @@ -1393,10 +1376,9 @@ do {									\
>  		b->iph.saddr = a4->s_addr;
>  		b->iph.daddr = c->ip4.addr_seen.s_addr;
>  
> -		if (check)
> -			b->iph.check = *check;
> -		else
> -			tcp_update_check_ip4(b);
> +		b->iph.check = check ? *check :
> +			       csum_ip4_header(b->iph.tot_len, IPPROTO_TCP,
> +					       b->iph.saddr, b->iph.daddr);
>  
>  		SET_TCP_HEADER_COMMON_V4_V6(b, conn, seq);
>  
> diff --git a/udp.c b/udp.c
> index 56b58bd8b43a..cd34f659210b 100644
> --- a/udp.c
> +++ b/udp.c
> @@ -270,23 +270,6 @@ static void udp_invert_portmap(struct udp_port_fwd *fwd)
>  	}
>  }
>  
> -/**
> - * udp_update_check4() - Update checksum with variable parts from stored one
> - * @buf:	L2 packet buffer with final IPv4 header
> - */
> -static void udp_update_check4(struct udp4_l2_buf_t *buf)
> -{
> -	uint32_t sum = L2_BUF_IP4_PSUM(IPPROTO_UDP);
> -
> -	sum += buf->iph.tot_len;
> -	sum += (buf->iph.saddr >> 16) & 0xffff;
> -	sum += buf->iph.saddr & 0xffff;
> -	sum += (buf->iph.daddr >> 16) & 0xffff;
> -	sum += buf->iph.daddr & 0xffff;
> -
> -	buf->iph.check = (uint16_t)~csum_fold(sum);
> -}
> -
>  /**
>   * udp_update_l2_buf() - Update L2 buffers with Ethernet and IPv4 addresses
>   * @eth_d:	Ethernet destination address, NULL if unchanged
> @@ -614,7 +597,8 @@ static size_t udp_update_hdr4(const struct ctx *c, int n, in_port_t dstport,
>  		b->iph.saddr = b->s_in.sin_addr.s_addr;
>  	}
>  
> -	udp_update_check4(b);
> +	b->iph.check = csum_ip4_header(b->iph.tot_len, IPPROTO_UDP,
> +				       b->iph.saddr, b->iph.daddr);
>  	b->uh.source = b->s_in.sin_port;
>  	b->uh.dest = htons(dstport);
>  	b->uh.len = htons(udp4_l2_mh_sock[n].msg_len + sizeof(b->uh));

-- 
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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