When building with Clang we encounter these warnings: | net/netfilter/xt_TPROXY.c:173:5: error: format specifies type 'unsigned | char' but the argument has type 'int' [-Werror,-Wformat] tproto, | &iph->saddr, ntohs(hp->source), - | net/netfilter/xt_TPROXY.c:181:4: error: format specifies type 'unsigned | char' but the argument has type 'int' [-Werror,-Wformat] tproto, | &iph->saddr, ntohs(hp->source), The format specifier `%hhu` refers to a u8 while tproto is an int. In this case we weren't losing any data because ipv6_find_hdr returns an int but its return value (nexthdr) is a u8. This u8 gets widened to an int when returned from ipv6_find_hdr and assigned to tproto. The previous format specifier is functionally fine but still produces a warning due to a type mismatch. The fix is simply to listen to Clang and change `%hhu` to `%d` for both instances of the warning. Link: https://github.com/ClangBuiltLinux/linux/issues/378 Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx> --- It should be noted that for this entire file to build without -Wformat warnings you should apply this `ntohs` patch which fixed many, many -Wformat warnings in the kernel. https://lore.kernel.org/all/20220608223539.470472-1-justinstitt@xxxxxxxxxx/ net/netfilter/xt_TPROXY.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/netfilter/xt_TPROXY.c b/net/netfilter/xt_TPROXY.c index 459d0696c91a..5d74abffc94f 100644 --- a/net/netfilter/xt_TPROXY.c +++ b/net/netfilter/xt_TPROXY.c @@ -169,7 +169,7 @@ tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par) targets on the same rule yet */ skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value; - pr_debug("redirecting: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n", + pr_debug("redirecting: proto %d %pI6:%hu -> %pI6:%hu, mark: %x\n", tproto, &iph->saddr, ntohs(hp->source), laddr, ntohs(lport), skb->mark); @@ -177,7 +177,7 @@ tproxy_tg6_v1(struct sk_buff *skb, const struct xt_action_param *par) return NF_ACCEPT; } - pr_debug("no socket, dropping: proto %hhu %pI6:%hu -> %pI6:%hu, mark: %x\n", + pr_debug("no socket, dropping: proto %d %pI6:%hu -> %pI6:%hu, mark: %x\n", tproto, &iph->saddr, ntohs(hp->source), &iph->daddr, ntohs(hp->dest), skb->mark); -- 2.37.0.rc0.161.g10f37bed90-goog
