From 7df624e79a450ba6b737b972040d9007ecc61672 Mon Sep 17 00:00:00 2001 From: Laurent Vivier Date: Wed, 6 Mar 2024 16:58:36 +1100 Subject: [PATCH] checksum: introduce functions to compute the header part checksum for TCP/UDP 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 Message-ID: <20240303135114.1023026-8-lvivier@redhat.com> Signed-off-by: David Gibson Signed-off-by: Stefano Brivio --- 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 1ac7975..f8a7b53 100644 --- a/checksum.c +++ b/checksum.c @@ -137,6 +137,29 @@ 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) + * @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 @@ -153,14 +176,10 @@ 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); } } @@ -183,6 +202,27 @@ 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 @@ -193,14 +233,11 @@ 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 996f456..0f39676 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 *icmp4hr, 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 7fb9dba..a7156ee 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(const 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); + struct in_addr saddr = { .s_addr = iph->saddr }; + struct in_addr daddr = { .s_addr = iph->daddr }; + uint32_t sum = proto_ipv4_header_psum(tlen, IPPROTO_TCP, saddr, 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); + uint16_t payload_len = ntohs(ip6h->payload_len); + uint32_t sum = proto_ipv6_header_psum(payload_len, IPPROTO_TCP, + &ip6h->saddr, &ip6h->daddr); - buf->ip6h.hop_limit = IPPROTO_TCP; - buf->ip6h.version = 0; - buf->ip6h.nexthdr = 0; - - 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 fb8373b..2fd6792 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); }