From: David Gibson <david@gibson.dropbear.id.au>
To: Laurent Vivier <lvivier@redhat.com>
Cc: passt-dev@passt.top
Subject: Re: [PATCH v5 7/9] checksum: introduce functions to compute the header part checksum for TCP/UDP
Date: Mon, 4 Mar 2024 11:52:31 +1100 [thread overview]
Message-ID: <ZeUbTxiwBZFVhNVZ@zatzit> (raw)
In-Reply-To: <20240303135114.1023026-8-lvivier@redhat.com>
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On Sun, Mar 03, 2024 at 02:51:12PM +0100, Laurent Vivier wrote:
> The TCP and UDP checksums are computed using the data in the TCP/UDP
> payload but also some informations in the IP header (protocol,
> length, source and destination addresses).
>
> We add two functions, proto_ipv4_header_psum() and
> proto_ipv6_header_psum(), to compute the checksum of the IP
> header part.
>
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>
> Notes:
> v5:
> - use struct in_addr
> - update tcp_update_check_tcp4()/tcp_update_check_tcp6()
> function comment and add tcphdr as a parameter
>
> v4:
> - fix payload length endianness
>
> v3:
> - function parameters provide tot_len, saddr, daddr and protocol
> rather than an iphdr/ipv6hdr
>
> v2:
> - move new function to checksum.c
> - use _psum rather than _checksum in the name
> - replace csum_udp4() and csum_udp6() by the new function
>
> v5:
> - use struct in_addr
>
> v4:
> - fix payload length endianness
>
> v3:
> - function parameters provide tot_len, saddr, daddr and protocol
> rather than an iphdr/ipv6hdr
>
> v2:
> - move new function to checksum.c
> - use _psum rather than _checksum in the name
> - replace csum_udp4() and csum_udp6() by the new function
>
> checksum.c | 67 ++++++++++++++++++++++++++++++++++++++++++------------
> checksum.h | 5 ++++
> tcp.c | 50 +++++++++++++++++++---------------------
> udp.c | 18 ++++++++-------
> 4 files changed, 90 insertions(+), 50 deletions(-)
>
> diff --git a/checksum.c b/checksum.c
> index ad81a7104a07..7625d7a41303 100644
> --- a/checksum.c
> +++ b/checksum.c
> @@ -139,6 +139,29 @@ uint16_t csum_ip4_header(uint16_t tot_len, uint8_t protocol,
> return ~csum_fold(sum);
> }
>
> +/**
> + * proto_ipv4_header_psum() - Calculates the partial checksum of an
> + * IPv4 header for UDP or TCP
> + * @tot_len: IPv4 Payload length (host order)
> + * @proto: Protocol number (host order)
"host order" is meaningless here, because it's a single byte value.
That can be fixed in followup though.
> + * @saddr: Source address (network order)
> + * @daddr: Destination address (network order)
> + * Returns: Partial checksum of the IPv4 header
> + */
> +uint32_t proto_ipv4_header_psum(uint16_t tot_len, uint8_t protocol,
> + struct in_addr saddr, struct in_addr daddr)
> +{
> + uint32_t psum = htons(protocol);
> +
> + psum += (saddr.s_addr >> 16) & 0xffff;
> + psum += saddr.s_addr & 0xffff;
> + psum += (daddr.s_addr >> 16) & 0xffff;
> + psum += daddr.s_addr & 0xffff;
> + psum += htons(tot_len);
> +
> + return psum;
> +}
> +
> /**
> * csum_udp4() - Calculate and set checksum for a UDP over IPv4 packet
> * @udp4hr: UDP header, initialised apart from checksum
> @@ -155,14 +178,10 @@ void csum_udp4(struct udphdr *udp4hr,
> udp4hr->check = 0;
>
> if (UDP4_REAL_CHECKSUMS) {
> - /* UNTESTED: if we did want real UDPv4 checksums, this
> - * is roughly what we'd need */
> - uint32_t psum = csum_fold(saddr.s_addr)
> - + csum_fold(daddr.s_addr)
> - + htons(len + sizeof(*udp4hr))
> - + htons(IPPROTO_UDP);
> - /* Add in partial checksum for the UDP header alone */
> - psum += sum_16b(udp4hr, sizeof(*udp4hr));
> + uint16_t tot_len = len + sizeof(struct udphdr);
> + uint32_t psum = proto_ipv4_header_psum(tot_len, IPPROTO_UDP,
> + saddr, daddr);
> + psum = csum_unfolded(udp4hr, sizeof(struct udphdr), psum);
> udp4hr->check = csum(payload, len, psum);
> }
> }
> @@ -185,6 +204,27 @@ void csum_icmp4(struct icmphdr *icmp4hr, const void *payload, size_t len)
> icmp4hr->checksum = csum(payload, len, psum);
> }
>
> +/**
> + * proto_ipv6_header_psum() - Calculates the partial checksum of an
> + * IPv6 header for UDP or TCP
> + * @payload_len: IPv6 payload length (host order)
> + * @proto: Protocol number (host order)
> + * @saddr: Source address (network order)
> + * @daddr: Destination address (network order)
> + * Returns: Partial checksum of the IPv6 header
> + */
> +uint32_t proto_ipv6_header_psum(uint16_t payload_len, uint8_t protocol,
> + const struct in6_addr *saddr,
> + const struct in6_addr *daddr)
> +{
> + uint32_t sum = htons(protocol) + htons(payload_len);
> +
> + sum += sum_16b(saddr, sizeof(*saddr));
> + sum += sum_16b(daddr, sizeof(*daddr));
> +
> + return sum;
> +}
> +
> /**
> * csum_udp6() - Calculate and set checksum for a UDP over IPv6 packet
> * @udp6hr: UDP header, initialised apart from checksum
> @@ -195,14 +235,11 @@ void csum_udp6(struct udphdr *udp6hr,
> const struct in6_addr *saddr, const struct in6_addr *daddr,
> 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);
> -
> + uint32_t psum = proto_ipv6_header_psum(len + sizeof(struct udphdr),
> + IPPROTO_UDP, saddr, daddr);
> udp6hr->check = 0;
> - /* Add in partial checksum for the UDP header alone */
> - psum += sum_16b(udp6hr, sizeof(*udp6hr));
> +
> + psum = csum_unfolded(udp6hr, sizeof(struct udphdr), psum);
> udp6hr->check = csum(payload, len, psum);
> }
>
> diff --git a/checksum.h b/checksum.h
> index e990fefa7f39..d4e563c85f4f 100644
> --- a/checksum.h
> +++ b/checksum.h
> @@ -15,10 +15,15 @@ uint16_t csum_fold(uint32_t sum);
> uint16_t csum_unaligned(const void *buf, size_t len, uint32_t init);
> uint16_t csum_ip4_header(uint16_t tot_len, uint8_t protocol,
> struct in_addr saddr, struct in_addr daddr);
> +uint32_t proto_ipv4_header_psum(uint16_t tot_len, uint8_t protocol,
> + struct in_addr saddr, struct in_addr daddr);
> void csum_udp4(struct udphdr *udp4hr,
> struct in_addr saddr, struct in_addr daddr,
> const void *payload, size_t len);
> void csum_icmp4(struct icmphdr *ih, const void *payload, size_t len);
> +uint32_t proto_ipv6_header_psum(uint16_t payload_len, uint8_t protocol,
> + const struct in6_addr *saddr,
> + const struct in6_addr *daddr);
> void csum_udp6(struct udphdr *udp6hr,
> const struct in6_addr *saddr, const struct in6_addr *daddr,
> const void *payload, size_t len);
> diff --git a/tcp.c b/tcp.c
> index 7fb9dba95a6a..53da8b84780f 100644
> --- a/tcp.c
> +++ b/tcp.c
> @@ -937,41 +937,33 @@ static void tcp_sock_set_bufsize(const struct ctx *c, int s)
>
> /**
> * tcp_update_check_tcp4() - Update TCP checksum from stored one
> - * @buf: L2 packet buffer with final IPv4 header
> + * @iph: IPv4 header
> + * @th: TCP header followed by TCP payload
> */
> -static void tcp_update_check_tcp4(struct tcp4_l2_buf_t *buf)
> +static void tcp_update_check_tcp4(struct iphdr *iph, struct tcphdr *th)
> {
> - uint16_t tlen = ntohs(buf->iph.tot_len) - 20;
> - uint32_t sum = htons(IPPROTO_TCP);
> + uint16_t tlen = ntohs(iph->tot_len) - sizeof(struct iphdr);
> + uint32_t sum = proto_ipv4_header_psum(tlen, IPPROTO_TCP,
> + (struct in_addr){ .s_addr = iph->saddr },
> + (struct in_addr){ .s_addr = iph->daddr });
>
> - sum += (buf->iph.saddr >> 16) & 0xffff;
> - sum += buf->iph.saddr & 0xffff;
> - sum += (buf->iph.daddr >> 16) & 0xffff;
> - sum += buf->iph.daddr & 0xffff;
> - sum += htons(ntohs(buf->iph.tot_len) - 20);
> -
> - buf->th.check = 0;
> - buf->th.check = csum(&buf->th, tlen, sum);
> + th->check = 0;
> + th->check = csum(th, tlen, sum);
> }
>
> /**
> * tcp_update_check_tcp6() - Calculate TCP checksum for IPv6
> - * @buf: L2 packet buffer with final IPv6 header
> + * @ip6h: IPv6 header
> + * @th: TCP header followed by TCP payload
> */
> -static void tcp_update_check_tcp6(struct tcp6_l2_buf_t *buf)
> +static void tcp_update_check_tcp6(struct ipv6hdr *ip6h, struct tcphdr *th)
> {
> - int len = ntohs(buf->ip6h.payload_len) + sizeof(struct ipv6hdr);
> -
> - buf->ip6h.hop_limit = IPPROTO_TCP;
> - buf->ip6h.version = 0;
> - buf->ip6h.nexthdr = 0;
> + uint16_t payload_len = ntohs(ip6h->payload_len);
> + uint32_t sum = proto_ipv6_header_psum(payload_len, IPPROTO_TCP,
> + &ip6h->saddr, &ip6h->daddr);
>
> - buf->th.check = 0;
> - buf->th.check = csum(&buf->ip6h, len, 0);
> -
> - buf->ip6h.hop_limit = 255;
> - buf->ip6h.version = 6;
> - buf->ip6h.nexthdr = IPPROTO_TCP;
> + th->check = 0;
> + th->check = csum(th, payload_len, sum);
> }
>
> /**
> @@ -1383,7 +1375,7 @@ do { \
>
> SET_TCP_HEADER_COMMON_V4_V6(b, conn, seq);
>
> - tcp_update_check_tcp4(b);
> + tcp_update_check_tcp4(&b->iph, &b->th);
>
> tlen = tap_iov_len(c, &b->taph, ip_len);
> } else {
> @@ -1402,7 +1394,11 @@ do { \
>
> SET_TCP_HEADER_COMMON_V4_V6(b, conn, seq);
>
> - tcp_update_check_tcp6(b);
> + tcp_update_check_tcp6(&b->ip6h, &b->th);
> +
> + b->ip6h.hop_limit = 255;
> + b->ip6h.version = 6;
> + b->ip6h.nexthdr = IPPROTO_TCP;
>
> b->ip6h.flow_lbl[0] = (conn->sock >> 16) & 0xf;
> b->ip6h.flow_lbl[1] = (conn->sock >> 8) & 0xff;
> diff --git a/udp.c b/udp.c
> index fb8373beba40..2fd67925f368 100644
> --- a/udp.c
> +++ b/udp.c
> @@ -625,6 +625,7 @@ static size_t udp_update_hdr6(const struct ctx *c, int n, in_port_t dstport,
> {
> struct udp6_l2_buf_t *b = &udp6_l2_buf[n];
> const struct in6_addr *src, *dst;
> + uint16_t payload_len;
> in_port_t src_port;
> size_t ip_len;
>
> @@ -634,7 +635,8 @@ static size_t udp_update_hdr6(const struct ctx *c, int n, in_port_t dstport,
>
> ip_len = udp6_l2_mh_sock[n].msg_len + sizeof(b->ip6h) + sizeof(b->uh);
>
> - b->ip6h.payload_len = htons(udp6_l2_mh_sock[n].msg_len + sizeof(b->uh));
> + payload_len = udp6_l2_mh_sock[n].msg_len + sizeof(b->uh);
> + b->ip6h.payload_len = htons(payload_len);
>
> if (IN6_IS_ADDR_LINKLOCAL(src)) {
> dst = &c->ip6.addr_ll_seen;
> @@ -670,17 +672,17 @@ static size_t udp_update_hdr6(const struct ctx *c, int n, in_port_t dstport,
> }
> b->ip6h.daddr = *dst;
> b->ip6h.saddr = *src;
> + b->ip6h.version = 6;
> + b->ip6h.nexthdr = IPPROTO_UDP;
> + b->ip6h.hop_limit = 255;
>
> b->uh.source = b->s_in6.sin6_port;
> b->uh.dest = htons(dstport);
> b->uh.len = b->ip6h.payload_len;
> -
> - b->ip6h.hop_limit = IPPROTO_UDP;
> - b->ip6h.version = b->ip6h.nexthdr = b->uh.check = 0;
> - b->uh.check = csum(&b->ip6h, ip_len, 0);
> - b->ip6h.version = 6;
> - b->ip6h.nexthdr = IPPROTO_UDP;
> - b->ip6h.hop_limit = 255;
> + b->uh.check = 0;
> + b->uh.check = csum(&b->uh, payload_len,
> + proto_ipv6_header_psum(payload_len, IPPROTO_UDP,
> + src, dst));
>
> return tap_iov_len(c, &b->taph, ip_len);
> }
--
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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next prev parent reply other threads:[~2024-03-04 0:55 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-03 13:51 [PATCH v5 0/9] Add vhost-user support to passt (part 1) Laurent Vivier
2024-03-03 13:51 ` [PATCH v5 1/9] pcap: add pcap_iov() Laurent Vivier
2024-03-03 13:51 ` [PATCH v5 2/9] checksum: align buffers Laurent Vivier
2024-03-03 13:51 ` [PATCH v5 3/9] checksum: add csum_iov() Laurent Vivier
2024-03-03 13:51 ` [PATCH v5 4/9] util: move IP stuff from util.[ch] to ip.[ch] Laurent Vivier
2024-03-03 13:51 ` [PATCH v5 5/9] udp: little cleanup in udp_update_hdrX() to prepare future changes Laurent Vivier
2024-03-04 0:46 ` David Gibson
2024-03-03 13:51 ` [PATCH v5 6/9] checksum: use csum_ip4_header() in udp.c and tcp.c Laurent Vivier
2024-03-03 13:51 ` [PATCH v5 7/9] checksum: introduce functions to compute the header part checksum for TCP/UDP Laurent Vivier
2024-03-04 0:52 ` David Gibson [this message]
2024-03-03 13:51 ` [PATCH v5 8/9] tap: make tap_update_mac() generic Laurent Vivier
2024-03-03 13:51 ` [PATCH v5 9/9] tcp: Introduce ipv4_fill_headers()/ipv6_fill_headers() Laurent Vivier
2024-03-04 0:54 ` David Gibson
2024-03-05 22:12 ` [PATCH v5 0/9] Add vhost-user support to passt (part 1) Stefano Brivio
2024-03-06 3:22 ` David Gibson
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