Now that ICMP pass-through from socket-to-tap is in place, it is easy to support UDP based traceroute functionality in direction tap-to-socket. We fix that in this commit. Link: https://bugs.passt.top/show_bug.cgi?id=64 Signed-off-by: Jon Maloy <jmaloy(a)redhat.com> --- v2: - Using ancillary data instead of setsockopt to transfer outgoing TTL. - Support IPv6 v3: - Storing ttl per packet instead of per flow. This may not be elegant, but much less intrusive than changing the flow criteria. This eliminates the need for the extra, flow-changing patch we introduced in v2. v4: - Going back to something similar to the original solution, but storing current ttl in struct udp_flow, plus ensuring that all packets in a struct tap4_l4_t/tap6_l4_t instance have the same ttl. After input from David Gibson. v5: - Some minor fixes after feedback from Stefano Brivio. v6: - Ensured that socket TTL is initialized at flow creation. - Ensured that setting of hop limit on IPv6 socket works. v7: - Setting of IPv6 hop_limit fails sometimes unless it is 4 bytes. --- tap.c | 17 +++++++++++++---- udp.c | 22 +++++++++++++++++++++- udp.h | 3 ++- udp_flow.c | 1 + udp_flow.h | 4 +++- 5 files changed, 40 insertions(+), 7 deletions(-) diff --git a/tap.c b/tap.c index 3a6fcbe..d630f6d 100644 --- a/tap.c +++ b/tap.c @@ -559,6 +559,7 @@ PACKET_POOL_DECL(pool_l4, UIO_MAXIOV, pkt_buf); * struct l4_seq4_t - Message sequence for one protocol handler call, IPv4 * @msgs: Count of messages in sequence * @protocol: Protocol number + * @ttl: Time to live * @source: Source port * @dest: Destination port * @saddr: Source address @@ -567,6 +568,7 @@ PACKET_POOL_DECL(pool_l4, UIO_MAXIOV, pkt_buf); */ static struct tap4_l4_t { uint8_t protocol; + uint8_t ttl; uint16_t source; uint16_t dest; @@ -586,6 +588,7 @@ static struct tap4_l4_t { * @dest: Destination port * @saddr: Source address * @daddr: Destination address + * @hop_limit: Hop limit * @msg: Array of messages that can be handled in a single call */ static struct tap6_l4_t { @@ -598,6 +601,8 @@ static struct tap6_l4_t { struct in6_addr saddr; struct in6_addr daddr; + uint8_t hop_limit; + struct pool_l4_t p; } tap6_l4[TAP_SEQS /* Arbitrary: TAP_MSGS in theory, so limit in users */]; @@ -786,7 +791,8 @@ resume: #define L4_MATCH(iph, uh, seq) \ ((seq)->protocol == (iph)->protocol && \ (seq)->source == (uh)->source && (seq)->dest == (uh)->dest && \ - (seq)->saddr.s_addr == (iph)->saddr && (seq)->daddr.s_addr == (iph)->daddr) + (seq)->saddr.s_addr == (iph)->saddr && \ + (seq)->daddr.s_addr == (iph)->daddr && (seq)->ttl == (iph)->ttl) #define L4_SET(iph, uh, seq) \ do { \ @@ -795,6 +801,7 @@ resume: (seq)->dest = (uh)->dest; \ (seq)->saddr.s_addr = (iph)->saddr; \ (seq)->daddr.s_addr = (iph)->daddr; \ + (seq)->ttl = (iph)->ttl; \ } while (0) if (seq && L4_MATCH(iph, uh, seq) && seq->p.count < UIO_MAXIOV) @@ -843,7 +850,7 @@ append: for (k = 0; k < p->count; ) k += udp_tap_handler(c, PIF_TAP, AF_INET, &seq->saddr, &seq->daddr, - p, k, now); + seq->ttl, p, k, now); } } @@ -966,7 +973,8 @@ resume: (seq)->dest == (uh)->dest && \ (seq)->flow_lbl == ip6_get_flow_lbl(ip6h) && \ IN6_ARE_ADDR_EQUAL(&(seq)->saddr, saddr) && \ - IN6_ARE_ADDR_EQUAL(&(seq)->daddr, daddr)) + IN6_ARE_ADDR_EQUAL(&(seq)->daddr, daddr) && \ + (seq)->hop_limit == (ip6h)->hop_limit) #define L4_SET(ip6h, proto, uh, seq) \ do { \ @@ -976,6 +984,7 @@ resume: (seq)->flow_lbl = ip6_get_flow_lbl(ip6h); \ (seq)->saddr = *saddr; \ (seq)->daddr = *daddr; \ + (seq)->hop_limit = (ip6h)->hop_limit; \ } while (0) if (seq && L4_MATCH(ip6h, proto, uh, seq) && @@ -1026,7 +1035,7 @@ append: for (k = 0; k < p->count; ) k += udp_tap_handler(c, PIF_TAP, AF_INET6, &seq->saddr, &seq->daddr, - p, k, now); + seq->hop_limit, p, k, now); } } diff --git a/udp.c b/udp.c index b275db3..3600336 100644 --- a/udp.c +++ b/udp.c @@ -818,6 +818,7 @@ fail: * @af: Address family, AF_INET or AF_INET6 * @saddr: Source address * @daddr: Destination address + * @ttl: TTL or hop limit for packets to be sent in this call * @p: Pool of UDP packets, with UDP headers * @idx: Index of first packet to process * @now: Current timestamp @@ -828,7 +829,8 @@ fail: */ int udp_tap_handler(const struct ctx *c, uint8_t pif, sa_family_t af, const void *saddr, const void *daddr, - const struct pool *p, int idx, const struct timespec *now) + uint8_t ttl, const struct pool *p, int idx, + const struct timespec *now) { const struct flowside *toside; struct mmsghdr mm[UIO_MAXIOV]; @@ -907,6 +909,24 @@ int udp_tap_handler(const struct ctx *c, uint8_t pif, mm[i].msg_hdr.msg_controllen = 0; mm[i].msg_hdr.msg_flags = 0; + if (ttl != uflow->ttl[tosidx.sidei]) { + uflow->ttl[tosidx.sidei] = ttl; + if (af == AF_INET) { + if (setsockopt(s, IPPROTO_IP, IP_TTL, + &ttl, sizeof(ttl)) < 0) + flow_perror(uflow, + "setsockopt IP_TTL"); + } else { + /* IPv6 hop_limit cannot be only 1 byte */ + int hop_limit = ttl; + + if (setsockopt(s, SOL_IPV6, IPV6_UNICAST_HOPS, + &hop_limit, sizeof(hop_limit)) < 0) + flow_perror(uflow, + "setsockopt IPV6_UNICAST_HOPS"); + } + } + count++; } diff --git a/udp.h b/udp.h index 8fc4283..8f8531a 100644 --- a/udp.h +++ b/udp.h @@ -15,7 +15,8 @@ void udp_sock_handler(const struct ctx *c, union epoll_ref ref, uint32_t events, const struct timespec *now); int udp_tap_handler(const struct ctx *c, uint8_t pif, sa_family_t af, const void *saddr, const void *daddr, - const struct pool *p, int idx, const struct timespec *now); + uint8_t ttl, const struct pool *p, int idx, + const struct timespec *now); int udp_sock_init(const struct ctx *c, int ns, const union inany_addr *addr, const char *ifname, in_port_t port); int udp_init(struct ctx *c); diff --git a/udp_flow.c b/udp_flow.c index af15d7f..d84d170 100644 --- a/udp_flow.c +++ b/udp_flow.c @@ -136,6 +136,7 @@ static flow_sidx_t udp_flow_new(const struct ctx *c, union flow *flow, uflow = FLOW_SET_TYPE(flow, FLOW_UDP, udp); uflow->ts = now->tv_sec; uflow->s[INISIDE] = uflow->s[TGTSIDE] = -1; + uflow->ttl[INISIDE] = uflow->ttl[TGTSIDE] = 0; flow_foreach_sidei(sidei) { if (pif_is_socket(uflow->f.pif[sidei])) diff --git a/udp_flow.h b/udp_flow.h index d518737..90d3b29 100644 --- a/udp_flow.h +++ b/udp_flow.h @@ -8,13 +8,14 @@ #define UDP_FLOW_H /** - * struct udp - Descriptor for a flow of UDP packets + * struct udp_flow - Descriptor for a flow of UDP packets * @f: Generic flow information * @closed: Flow is already closed * @flush0: @s[0] may have datagrams queued for other flows * @flush1: @s[1] may have datagrams queued for other flows * @ts: Activity timestamp * @s: Socket fd (or -1) for each side of the flow + * @ttl: TTL or hop_limit for both sides */ struct udp_flow { /* Must be first element */ @@ -24,6 +25,7 @@ struct udp_flow { bool flush0, flush1 :1; time_t ts; int s[SIDES]; + uint8_t ttl[SIDES]; }; struct udp_flow *udp_at_sidx(flow_sidx_t sidx); -- 2.48.1