Re: [PATCH v3 06/14] ip: Add ipproto_name() function

9 Jan 2026

On Thu, Jan 08, 2026 at 02:22:21PM +0100, Laurent Vivier wrote:
...
On 1/8/26 03:29, David Gibson wrote:
...
Add a function to get the name of an IP protocol from its number.  Usually
this would be done by getprotobynumber(), but that requires access to
/etc/protocols and might allocate.  We can't do either of those once we've
self-isolated.
Signed-off-by: David Gibson 
---
  ip.c | 27 +++++++++++++++++++++++++++
  ip.h |  2 ++
  2 files changed, 29 insertions(+)

diff --git a/ip.c b/ip.c
index 9a7f4c54..f1d224bd 100644
--- a/ip.c
+++ b/ip.c
@@ -67,3 +67,30 @@ found:
  *proto = nh;
  return true;
  }
+
+/**
+ * ipproto_name() - Get IP protocol name from number
+ * @proto:	IP protocol number
+ *
+ * Return: pointer to name of protocol @proto
+ *
+ * Usually this would be done with getprotobynumber(3) but that reads
+ * /etc/protocols and might allocate, which isn't possible for us once
+ * self-isolated.
+ */
+/* cppcheck-suppress unusedFunction */
+const char *ipproto_name(uint8_t proto)
+{
+	switch (proto) {
+	case IPPROTO_ICMP:
+		return "ICMP";
+	case IPPROTO_TCP:
+		return "TCP";
+	case IPPROTO_UDP:
+		return "UDP";
+	case IPPROTO_ICMPV6:
+		return "ICMPv6";
+	default:
+		return "<unknown protocol>";
+	}
+}
diff --git a/ip.h b/ip.h
index 5830b923..42b417c5 100644
--- a/ip.h
+++ b/ip.h
@@ -116,6 +116,7 @@ static inline uint32_t ip6_get_flow_lbl(const struct ipv6hdr *ip6h)
  }
  bool ipv6_l4hdr(struct iov_tail *data, uint8_t *proto, size_t *dlen);
+const char *ipproto_name(uint8_t proto);
  /* IPv6 link-local all-nodes multicast address, ff02::1 */
  static const struct in6_addr in6addr_ll_all_nodes = {
@@ -135,4 +136,5 @@ static const struct in_addr in4addr_broadcast = { 0xffffffff };
  #define IPV6_MIN_MTU		1280
  #endif
+
Extra blank line
Oops, fixed.
...
...
#endif /* IP_H */
Reviewed-by: Laurent Vivier 
-- 
David Gibson (he or they)	| 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

    