On Tue, Aug 05, 2025 at 05:46:09PM +0200, Laurent Vivier wrote:
Use packet_data() and extract headers using IOV_REMOVE_HEADER() and iov_remove_header_() rather than packet_get().
Signed-off-by: Laurent Vivier
Reviewed-by: David Gibson
--- tcp.c | 31 ++++++++++++++++++++++++------- 1 file changed, 24 insertions(+), 7 deletions(-)
diff --git a/tcp.c b/tcp.c index 957b498db32d..f1048d7230c9 100644 --- a/tcp.c +++ b/tcp.c @@ -310,6 +310,16 @@ #include "tcp_buf.h" #include "tcp_vu.h"
+/* + * The size of TCP header (including options) is given by doff (Data Offset) + * that is a 4-bit value specifying the number of 32-bit words in the header. + * The maximum value of doff is 15 [(1 << 4) - 1]. + * The maximum length in bytes of options is 15 minus the number of 32-bit + * words in the minimal TCP header (5) multiplied by the length of a 32-bit + * word (4). + */ +#define OPTLEN_MAX (((1UL << 4) - 1 - 5) * 4UL) + #ifndef __USE_MISC /* From Linux UAPI, missing in netinet/tcp.h provided by musl */ struct tcp_repair_opt { @@ -1957,8 +1967,11 @@ int tcp_tap_handler(const struct ctx *c, uint8_t pif, sa_family_t af, const struct pool *p, int idx, const struct timespec *now) { struct tcp_tap_conn *conn; + struct tcphdr th_storage; const struct tcphdr *th; - size_t optlen, len; + char optsc[OPTLEN_MAX]; + struct iov_tail data; + size_t optlen, l4len; const char *opts; union flow *flow; flow_sidx_t sidx; @@ -1967,15 +1980,19 @@ int tcp_tap_handler(const struct ctx *c, uint8_t pif, sa_family_t af,
(void)pif;
- th = packet_get(p, idx, 0, sizeof(*th), &len); + if (!packet_data(p, idx, &data)) + return 1; + + l4len = iov_tail_size(&data); + + th = IOV_REMOVE_HEADER(&data, th_storage); if (!th) return 1; - len += sizeof(*th);
optlen = th->doff * 4UL - sizeof(*th); /* Static checkers might fail to see this: */ - optlen = MIN(optlen, ((1UL << 4) /* from doff width */ - 6) * 4UL); - opts = packet_get(p, idx, sizeof(*th), optlen, NULL); + optlen = MIN(optlen, OPTLEN_MAX);
Pre-exisitng, but should we just drop packets with too many options, rather than truncating the options?
+ opts = (char *)iov_remove_header_(&data, &optsc[0], optlen, 1);
sidx = flow_lookup_af(c, IPPROTO_TCP, PIF_TAP, af, saddr, daddr, ntohs(th->source), ntohs(th->dest)); @@ -1987,7 +2004,7 @@ int tcp_tap_handler(const struct ctx *c, uint8_t pif, sa_family_t af, tcp_conn_from_tap(c, af, saddr, daddr, th, opts, optlen, now); else - tcp_rst_no_conn(c, af, saddr, daddr, flow_lbl, th, len); + tcp_rst_no_conn(c, af, saddr, daddr, flow_lbl, th, l4len); return 1; }
@@ -1995,7 +2012,7 @@ int tcp_tap_handler(const struct ctx *c, uint8_t pif, sa_family_t af, ASSERT(pif_at_sidx(sidx) == PIF_TAP); conn = &flow->tcp;
- flow_trace(conn, "packet length %zu from tap", len); + flow_trace(conn, "packet length %zu from tap", l4len);
if (th->rst) { conn_event(c, conn, CLOSED);
-- 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