Re: [PATCH 04/22] treewide: Use struct assignment instead of memcpy() for IP addresses

[Stefano Brivio <sbrivio@redhat.com>]

On Fri, 16 Aug 2024 15:39:45 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:

> We rely on C11 already, so we can use clearer and more type-checkable
> struct assignment instead of mempcy() for copying IP addresses around.
> 
> This exposes some "pointer could be const" warnings from cppcheck, so
> address those too.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  conf.c   | 12 ++++++------
>  dhcpv6.c | 10 ++++++----
>  2 files changed, 12 insertions(+), 10 deletions(-)
> 
> diff --git a/conf.c b/conf.c
> index 750fdc86..9b05afeb 100644
> --- a/conf.c
> +++ b/conf.c
> @@ -389,14 +389,14 @@ static void add_dns6(struct ctx *c,
>  	/* Guest or container can only access local addresses via redirect */
>  	if (IN6_IS_ADDR_LOOPBACK(addr)) {
>  		if (!c->no_map_gw) {
> -			memcpy(*conf, &c->ip6.gw, sizeof(**conf));
> +			**conf = c->ip6.gw;
>  			(*conf)++;
>  
>  			if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.dns_match))
> -				memcpy(&c->ip6.dns_match, addr, sizeof(*addr));
> +				c->ip6.dns_match = *addr;
>  		}
>  	} else {
> -		memcpy(*conf, addr, sizeof(**conf));
> +		**conf = *addr;
>  		(*conf)++;
>  	}
>  
> @@ -632,7 +632,7 @@ static unsigned int conf_ip4(unsigned int ifi,
>  			ip4->prefix_len = 32;
>  	}
>  
> -	memcpy(&ip4->addr_seen, &ip4->addr, sizeof(ip4->addr_seen));
> +	ip4->addr_seen = ip4->addr;
>  
>  	if (MAC_IS_ZERO(mac)) {
>  		int rc = nl_link_get_mac(nl_sock, ifi, mac);
> @@ -693,8 +693,8 @@ static unsigned int conf_ip6(unsigned int ifi,
>  		return 0;
>  	}
>  
> -	memcpy(&ip6->addr_seen, &ip6->addr, sizeof(ip6->addr));
> -	memcpy(&ip6->addr_ll_seen, &ip6->addr_ll, sizeof(ip6->addr_ll));
> +	ip6->addr_seen = ip6->addr;
> +	ip6->addr_ll_seen = ip6->addr_ll;
>  
>  	if (MAC_IS_ZERO(mac)) {
>  		rc = nl_link_get_mac(nl_sock, ifi, mac);
> diff --git a/dhcpv6.c b/dhcpv6.c
> index bbed41dc..87b3c3eb 100644
> --- a/dhcpv6.c
> +++ b/dhcpv6.c
> @@ -298,7 +298,8 @@ static struct opt_hdr *dhcpv6_ia_notonlink(const struct pool *p,
>  {
>  	char buf[INET6_ADDRSTRLEN];
>  	struct in6_addr req_addr;
> -	struct opt_hdr *ia, *h;
> +	const struct opt_hdr *h;
> +	struct opt_hdr *ia;
>  	size_t offset;
>  	int ia_type;
>  
> @@ -312,12 +313,13 @@ ia_ta:
>  		offset += sizeof(struct opt_ia_na);
>  
>  		while ((h = dhcpv6_opt(p, &offset, OPT_IAAADR))) {
> -			struct opt_ia_addr *opt_addr = (struct opt_ia_addr *)h;
> +			const struct opt_ia_addr *opt_addr
> +				= (const struct opt_ia_addr *)h;

Nit: the assignment could go on its own line, then?

>  			if (ntohs(h->l) != OPT_VSIZE(ia_addr))
>  				return NULL;
>  
> -			memcpy(&req_addr, &opt_addr->addr, sizeof(req_addr));
> +			req_addr = opt_addr->addr;
>  			if (!IN6_ARE_ADDR_EQUAL(la, &req_addr)) {
>  				info("DHCPv6: requested address %s not on link",
>  				     inet_ntop(AF_INET6, &req_addr,
> @@ -363,7 +365,7 @@ static size_t dhcpv6_dns_fill(const struct ctx *c, char *buf, int offset)
>  			srv->hdr.l = 0;
>  		}
>  
> -		memcpy(&srv->addr[i], &c->ip6.dns[i], sizeof(srv->addr[i]));
> +		srv->addr[i] = c->ip6.dns[i];
>  		srv->hdr.l += sizeof(srv->addr[i]);
>  		offset += sizeof(srv->addr[i]);
>  	}

I only reviewed up to this patch so far.

-- 
Stefano