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From: David Gibson <david@gibson.dropbear.id.au>
To: Laurent Vivier <lvivier@redhat.com>
Cc: passt-dev@passt.top
Subject: Re: [PATCH v4 5/8] checksum: use csum_ip4_header() in udp.c and tcp.c
Date: Fri, 1 Mar 2024 10:25:02 +1100	[thread overview]
Message-ID: <ZeESTj6olXE6NGti@zatzit> (raw)
In-Reply-To: <20240229165955.829476-6-lvivier@redhat.com>

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On Thu, Feb 29, 2024 at 05:59:52PM +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:
>     v4:
>       - rebase
>     
>     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

Function comment needs to be updated for the new parameters.  In
particular it needs to note that tot_len, saddr and daddr are all
passed in network order.

As noted elsewhere, I kind of hate passing non-host-endian values in
plain integer types, but I can see why doing otherwise here would be
very awkward.

>   */
> -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 d35d8944fc41..d4649f0167ab 100644
> --- a/tap.c
> +++ b/tap.c
> @@ -161,7 +161,8 @@ 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 e0588f92e65f..ea0802c6b102 100644
> --- a/tcp.c
> +++ b/tcp.c
> @@ -935,23 +935,6 @@ 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
> @@ -1394,10 +1377,9 @@ 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 26774df7018c..d517c99dcc69 100644
> --- a/udp.c
> +++ b/udp.c
> @@ -275,23 +275,6 @@ static void udp_invert_portmap(struct udp_fwd_ports *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
> @@ -619,7 +602,8 @@ static size_t udp_update_hdr4(const struct ctx *c, int n, in_port_t dstport,
>  		b->iph.saddr = src->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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  reply	other threads:[~2024-02-29 23:42 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-02-29 16:59 [PATCH v4 0/8] Add vhost-user support to passt (part 1) Laurent Vivier
2024-02-29 16:59 ` [PATCH v4 1/8] pcap: add pcap_iov() Laurent Vivier
2024-02-29 23:16   ` David Gibson
2024-02-29 16:59 ` [PATCH v4 2/8] checksum: align buffers Laurent Vivier
2024-02-29 16:59 ` [PATCH v4 3/8] checksum: add csum_iov() Laurent Vivier
2024-02-29 16:59 ` [PATCH v4 4/8] util: move IP stuff from util.[ch] to ip.[ch] Laurent Vivier
2024-02-29 23:19   ` David Gibson
2024-03-01 12:06     ` Laurent Vivier
2024-02-29 16:59 ` [PATCH v4 5/8] checksum: use csum_ip4_header() in udp.c and tcp.c Laurent Vivier
2024-02-29 23:25   ` David Gibson [this message]
2024-03-01 12:31     ` Laurent Vivier
2024-02-29 16:59 ` [PATCH v4 6/8] checksum: introduce functions to compute the header part checksum for TCP/UDP Laurent Vivier
2024-02-29 23:42   ` David Gibson
2024-02-29 16:59 ` [PATCH v4 7/8] tap: make tap_update_mac() generic Laurent Vivier
2024-02-29 16:59 ` [PATCH v4 8/8] tcp: Introduce ipv4_fill_headers()/ipv6_fill_headers() Laurent Vivier
2024-02-29 23:54   ` David Gibson
2024-03-03 13:50     ` Laurent Vivier

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