At least two places in passt calculate ICMPv6 checksums, ndp() and
tap_ip_send(). Add a helper to handle this calculation in both places.
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 ICMPv6 header and payload to
be in separate buffers, although we don't use this yet.
Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
---
checksum.c | 25 +++++++++++++++++++++++++
checksum.h | 5 +++++
ndp.c | 5 +----
tap.c | 6 ++----
4 files changed, 33 insertions(+), 8 deletions(-)
diff --git a/checksum.c b/checksum.c
index 56ad01e..78c6960 100644
--- a/checksum.c
+++ b/checksum.c
@@ -52,6 +52,8 @@
#include <stddef.h>
#include <stdint.h>
+#include <linux/icmpv6.h>
+
/**
* sum_16b() - Calculate sum of 16-bit words
* @buf: Input buffer
@@ -105,6 +107,29 @@ uint16_t csum_unaligned(const void *buf, size_t len, uint32_t init)
return (uint16_t)~csum_fold(sum_16b(buf, len) + init);
}
+/**
+ * csum_icmp6() - Calculate and set checksum for an ICMPv6 packet
+ * @icmp6hr: ICMPv6 header, initialised apart from checksum
+ * @saddr: IPv6 source address
+ * @daddr: IPv6 destination address
+ * @payload: ICMP packet payload
+ * @len: Length of @payload (not including ICMPv6 header)
+ */
+void csum_icmp6(struct icmp6hdr *icmp6hr,
+ 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(*icmp6hr)) + htons(IPPROTO_ICMPV6);
+
+ icmp6hr->icmp6_cksum = 0;
+ /* Add in partial checksum for the ICMPv6 header alone */
+ psum += sum_16b(icmp6hr, sizeof(*icmp6hr));
+ icmp6hr->icmp6_cksum = csum_unaligned(payload, len, psum);
+}
+
/**
* csum_tcp4() - Calculate TCP checksum for IPv4 and set in place
* @iph: Packet buffer, IP header
diff --git a/checksum.h b/checksum.h
index 5418406..d7daabf 100644
--- a/checksum.h
+++ b/checksum.h
@@ -6,9 +6,14 @@
#ifndef CHECKSUM_H
#define CHECKSUM_H
+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_icmp6(struct icmp6hdr *icmp6hr,
+ const struct in6_addr *saddr, const struct in6_addr *daddr,
+ const void *payload, size_t len);
void csum_tcp4(struct iphdr *iph);
uint16_t csum(const void *buf, size_t len, uint32_t init);
diff --git a/ndp.c b/ndp.c
index dec36a9..03f1d06 100644
--- a/ndp.c
+++ b/ndp.c
@@ -189,10 +189,7 @@ dns_done:
ip6hr->saddr = c->ip6.addr_ll;
ip6hr->payload_len = htons(sizeof(*ihr) + len);
- ip6hr->hop_limit = IPPROTO_ICMPV6;
- ihr->icmp6_cksum = 0;
- ihr->icmp6_cksum = csum_unaligned(ip6hr, sizeof(*ip6hr) +
- sizeof(*ihr) + len, 0);
+ csum_icmp6(ihr, &ip6hr->saddr, &ip6hr->daddr, ihr + 1, len);
ip6hr->version = 6;
ip6hr->nexthdr = IPPROTO_ICMPV6;
diff --git a/tap.c b/tap.c
index 8b6d9bc..aafc92b 100644
--- a/tap.c
+++ b/tap.c
@@ -191,10 +191,8 @@ void tap_ip_send(const struct ctx *c, const struct in6_addr *src,
uint8_t proto,
} else if (proto == IPPROTO_ICMPV6) {
struct icmp6hdr *ih = (struct icmp6hdr *)(ip6h + 1);
- ih->icmp6_cksum = 0;
- ih->icmp6_cksum = csum_unaligned(ip6h,
- len + sizeof(*ip6h),
- 0);
+ csum_icmp6(ih, &ip6h->saddr, &ip6h->daddr,
+ ih + 1, len - sizeof(*ih));
}
ip6h->version = 6;
ip6h->nexthdr = proto;
--
2.37.3