net: ipv6: ioam6: new feature tunsrc

This patch provides a new feature (i.e., "tunsrc") for the tunnel (i.e.,
"encap") mode of ioam6. Just like seg6 already does, except it is
attached to a route. The "tunsrc" is optional: when not provided (by
default), the automatic resolution is applied. Using "tunsrc" when
possible has a benefit: performance. See the comparison:
- before (= "encap" mode): https://ibb.co/bNCzvf7
- after (= "encap" mode with "tunsrc"): https://ibb.co/PT8L6yq

Signed-off-by: Justin Iurman <[e-mail]>
Signed-off-by: Paolo Abeni <[e-mail]>

include/uapi/linux/ioam6_iptunnel.h

···
 	IOAM6_IPTUNNEL_FREQ_K,		/* u32 */
 	IOAM6_IPTUNNEL_FREQ_N,		/* u32 */
 
+	/* Tunnel src address.
+	 * For encap,auto modes.
+	 * Optional (automatic if not provided).
+	 */
+	IOAM6_IPTUNNEL_SRC,		/* struct in6_addr */
+
 	__IOAM6_IPTUNNEL_MAX,
 };
 

net/ipv6/ioam6_iptunnel.c

···
 	struct ioam6_lwt_freq freq;
 	atomic_t pkt_cnt;
 	u8 mode;
+	bool has_tunsrc;
+	struct in6_addr tunsrc;
 	struct in6_addr tundst;
 	struct ioam6_lwt_encap tuninfo;
 };
···
 	[IOAM6_IPTUNNEL_MODE]	= NLA_POLICY_RANGE(NLA_U8,
 						   IOAM6_IPTUNNEL_MODE_MIN,
 						   IOAM6_IPTUNNEL_MODE_MAX),
+	[IOAM6_IPTUNNEL_SRC]	= NLA_POLICY_EXACT_LEN(sizeof(struct in6_addr)),
 	[IOAM6_IPTUNNEL_DST]	= NLA_POLICY_EXACT_LEN(sizeof(struct in6_addr)),
 	[IOAM6_IPTUNNEL_TRACE]	= NLA_POLICY_EXACT_LEN(
 					sizeof(struct ioam6_trace_hdr)),
···
 	else
 		mode = nla_get_u8(tb[IOAM6_IPTUNNEL_MODE]);
 
+	if (tb[IOAM6_IPTUNNEL_SRC] && mode == IOAM6_IPTUNNEL_MODE_INLINE) {
+		NL_SET_ERR_MSG(extack, "no tunnel src expected with this mode");
+		return -EINVAL;
+	}
+
 	if (!tb[IOAM6_IPTUNNEL_DST] && mode != IOAM6_IPTUNNEL_MODE_INLINE) {
 		NL_SET_ERR_MSG(extack, "this mode needs a tunnel destination");
 		return -EINVAL;
···
 
 	ilwt = ioam6_lwt_state(lwt);
 	err = dst_cache_init(&ilwt->cache, GFP_ATOMIC);
-	if (err) {
-		kfree(lwt);
-		return err;
-	}
+	if (err)
+		goto free_lwt;
 
 	atomic_set(&ilwt->pkt_cnt, 0);
 	ilwt->freq.k = freq_k;
 	ilwt->freq.n = freq_n;
 
 	ilwt->mode = mode;
+
+	if (!tb[IOAM6_IPTUNNEL_SRC]) {
+		ilwt->has_tunsrc = false;
+	} else {
+		ilwt->has_tunsrc = true;
+		ilwt->tunsrc = nla_get_in6_addr(tb[IOAM6_IPTUNNEL_SRC]);
+
+		if (ipv6_addr_any(&ilwt->tunsrc)) {
+			NL_SET_ERR_MSG_ATTR(extack, tb[IOAM6_IPTUNNEL_SRC],
+					    "invalid tunnel source address");
+			err = -EINVAL;
+			goto free_cache;
+		}
+	}
+
 	if (tb[IOAM6_IPTUNNEL_DST])
 		ilwt->tundst = nla_get_in6_addr(tb[IOAM6_IPTUNNEL_DST]);
 
···
 	*ts = lwt;
 
 	return 0;
+free_cache:
+	dst_cache_destroy(&ilwt->cache);
+free_lwt:
+	kfree(lwt);
+	return err;
 }
 
 static int ioam6_do_fill(struct net *net, struct sk_buff *skb)
···
 
 static int ioam6_do_encap(struct net *net, struct sk_buff *skb,
 			  struct ioam6_lwt_encap *tuninfo,
+			  bool has_tunsrc,
+			  struct in6_addr *tunsrc,
 			  struct in6_addr *tundst)
 {
 	struct dst_entry *dst = skb_dst(skb);
···
 	hdr->nexthdr = NEXTHDR_HOP;
 	hdr->payload_len = cpu_to_be16(skb->len - sizeof(*hdr));
 	hdr->daddr = *tundst;
-	ipv6_dev_get_saddr(net, dst->dev, &hdr->daddr,
-			   IPV6_PREFER_SRC_PUBLIC, &hdr->saddr);
+
+	if (has_tunsrc)
+		memcpy(&hdr->saddr, tunsrc, sizeof(*tunsrc));
+	else
+		ipv6_dev_get_saddr(net, dst->dev, &hdr->daddr,
+				   IPV6_PREFER_SRC_PUBLIC, &hdr->saddr);
 
 	skb_postpush_rcsum(skb, hdr, len);
 
···
 	case IOAM6_IPTUNNEL_MODE_ENCAP:
 do_encap:
 		/* Encapsulation (ip6ip6) */
-		err = ioam6_do_encap(net, skb, &ilwt->tuninfo, &ilwt->tundst);
+		err = ioam6_do_encap(net, skb, &ilwt->tuninfo,
+				     ilwt->has_tunsrc, &ilwt->tunsrc,
+				     &ilwt->tundst);
 		if (unlikely(err))
 			goto drop;
 
···
 		goto ret;
 
 	if (ilwt->mode != IOAM6_IPTUNNEL_MODE_INLINE) {
+		if (ilwt->has_tunsrc) {
+			err = nla_put_in6_addr(skb, IOAM6_IPTUNNEL_SRC,
+					       &ilwt->tunsrc);
+			if (err)
+				goto ret;
+		}
+
 		err = nla_put_in6_addr(skb, IOAM6_IPTUNNEL_DST, &ilwt->tundst);
 		if (err)
 			goto ret;
···
 		  nla_total_size(sizeof(ilwt->mode)) +
 		  nla_total_size(sizeof(ilwt->tuninfo.traceh));
 
-	if (ilwt->mode != IOAM6_IPTUNNEL_MODE_INLINE)
+	if (ilwt->mode != IOAM6_IPTUNNEL_MODE_INLINE) {
+		if (ilwt->has_tunsrc)
+			nlsize += nla_total_size(sizeof(ilwt->tunsrc));
+
 		nlsize += nla_total_size(sizeof(ilwt->tundst));
+	}
 
 	return nlsize;
 }
···
 	return (ilwt_a->freq.k != ilwt_b->freq.k ||
 		ilwt_a->freq.n != ilwt_b->freq.n ||
 		ilwt_a->mode != ilwt_b->mode ||
+		ilwt_a->has_tunsrc != ilwt_b->has_tunsrc ||
 		(ilwt_a->mode != IOAM6_IPTUNNEL_MODE_INLINE &&
 		 !ipv6_addr_equal(&ilwt_a->tundst, &ilwt_b->tundst)) ||
+		(ilwt_a->mode != IOAM6_IPTUNNEL_MODE_INLINE &&
+		 ilwt_a->has_tunsrc &&
+		 !ipv6_addr_equal(&ilwt_a->tunsrc, &ilwt_b->tunsrc)) ||
 		trace_a->namespace_id != trace_b->namespace_id);
 }